Fluid-assisted medical devices, systems and methods

ABSTRACT

Adaptors for electrically coupling between an electrosurgical generator and a bipolar electrosurgical device are provided. In one preferred embodiment, the adaptor comprises a power input connector for coupling the adaptor with a monopolar mode power output connector of the electrosurgical generator, a ground connector for coupling the adaptor with a ground connector of the electrosurgical generator, a first and a second power output connector, each for coupling the adaptor with a first and a second bipolar mode power input connector of the bipolar electrosurgical device, respectively, a monopolar hand switch connector for coupling the adaptor with a monopolar mode hand switch connector of the electrosurgical generator, and at least one bipolar mode hand switch connector for coupling the adaptor with a bipolar mode hand switch connector of the electrosurgical device.

This application is being filed on 3 Mar. 2004, as a PCT internationalpatent application in the name of TissueLink Medical, Inc. (a U.S.national corporation), and David E. Lipson and David J. Flanagan (bothU.S. citizens.

FIELD

This invention relates generally to the field of medical devices andmethods for use upon a body during surgery. More particularly, theinvention relates to electrosurgical devices, systems and methods foruse upon tissues of a human body during surgery, particularly opensurgery and minimally invasive surgery such as laparoscopic surgery.

BACKGROUND

Electrosurgical devices configured for use with a dry tip use electricalenergy, often radio frequency (RF) energy, to cut tissue or to cauterizeblood vessels. During use, a voltage gradient is created at the tip ofthe device, thereby inducing current flow and related heat generation inthe tissue. With sufficiently high levels of electrical power, the heatgenerated is sufficient to cut the tissue and, advantageously, to stopthe bleeding from severed blood vessels.

Current dry tip electrosurgical devices can cause the temperature oftissue being treated to rise significantly higher than 100° C.,resulting in tissue desiccation, tissue sticking to the electrodes,tissue perforation, char formation and smoke generation. Desiccationoccurs when tissue temperature exceeds 100° C. and all of theintracellular water boils away, leaving the tissue extremely dry andmuch less electrically conductive. Peak temperatures of target tissue asa result of dry RF treatment can be as high as 320° C., and such hightemperatures can be transmitted to adjacent tissue via thermaldiffusion. Consequently, this may result in undesirable desiccation andthermal damage to the adjacent tissue.

The use of saline inhibits undesirable effects such as tissuedesiccation, electrode sticking, smoke production and char formation.However, an uncontrolled or abundant flow rate of saline can provide toomuch electrical dispersion and cooling at the electrode/tissueinterface. This reduces the temperature of the target tissue beingtreated, and, in turn, can result in longer treatment time to achievethe desired tissue temperature for treatment of the tissue. Longtreatment times are undesirable for surgeons since it is in the bestinterest of the patient, physician and hospital, to perform surgicalprocedures as quickly as possible.

RF power delivered to tissue can be less than optimal when usinggeneral-purpose generators. Most general-purpose RE generators havemodes for different waveforms (e.g., cut, coagulation, or blend) anddevice types (e.g., monopolar, bipolar), as well as power levels thatcan be set in watts. However, once these settings are chosen, the actualpower delivered to tissue and associated heat generated can varydramatically over time as tissue impedance changes during the course ofRF treatment. This is because the power delivered by most generators isa function of tissue impedance, with the power ramping down as impedanceeither decreases toward zero or increases significantly to severalthousand ohms. Current dry tip electrosurgical devices are notconfigured to address a change in power provided by the generator astissue impedance changes or the associated effect on tissue, and rely onthe surgeon's expertise to overcome this limitation.

SUMMARY OF THE INVENTION

The invention is directed to various embodiments of electrosurgicaldevices, systems and methods. In one preferred embodiment, anelectrosurgical device has a handle, a shaft extending from the handlehaving a distal end, and an electrode tip having an electrode surfacewith at least a portion of the electrode tip extending distally beyondthe distal end of the shaft. In one embodiment, preferably the portionof the electrode tip extending distally beyond the distal end of theshaft comprises a cone shaped portion. The device also has a fluidpassage being connectable to a fluid source and at least one fluidoutlet opening in fluid communication with the fluid passage.

In another preferred embodiment, the electrode tip extending distallybeyond the distal end of the shaft has a neck portion and an enlargedend portion with the enlarged end portion located distal to the neckportion and comprising the cone shaped portion.

In another preferred embodiment, the fluid outlet opening is arranged toprovide a fluid from the fluid source to the neck portion of theelectrode tip.

In yet another preferred embodiment, the fluid outlet opening isarranged to provide a fluid from the fluid source towards the enlargedend portion of the electrode tip.

In another preferred embodiment, an electrosurgical device has a handle,and an electrode tip having an electrode surface with the electrodesurface and comprising a cone shaped portion. The device also has afluid passage being connectable to a fluid source and at least one fluidoutlet opening in fluid communication with the fluid passage andarranged to provide a fluid from the fluid source to the cone shapedportion of the electrode tip.

The invention is also directed to a surgical method for treating tissue.The method includes providing tissue having a tissue surface, providingradio frequency power at a power level, providing an electricallyconductive fluid at a fluid flow rate, providing an surgical deviceconfigured to simultaneously provide the radio frequency electricalpower and the electrically conductive fluid to tissue, providing theelectrically conductive fluid to the tissue at the tissue surface,forming a fluid coupling comprising the electrically conductive fluidwhich couples the tissue and the surgical device, providing the radiofrequency power to the tissue at the tissue surface and below the tissuesurface into the tissue through the fluid coupling, coagulating thetissue without cutting the tissue, and dissecting the tissue aftercoagulating the tissue. Preferably, the device comprises an electrodetip having an electrode surface, and comprising a cone shaped portionand a distal end. Also preferably, coagulating the tissue is performedwith the cone shaped portion and dissecting is performed with the distalend of the device. In various embodiments, the dissection may be bluntas where the distal end of the device is blunt, or sharp as where thedistal end of the device is pointed.

The invention is also directed to various embodiments of an adaptor forelectrically coupling between an electrosurgical generator and a bipolarelectrosurgical device. In one preferred embodiment, the adaptorcomprises a power input connector for coupling the adaptor with amonopolar mode power output connector of the electrosurgical generator,a ground connector for coupling the adaptor with a ground connector ofthe electrosurgical generator, a first and a second power outputconnector, each for coupling the adaptor with a first and a secondbipolar mode power input connector of the bipolar electrosurgicaldevice, respectively, a transformer coupled between the power inputconnector and the first and second power output connectors, a monopolarhand switch connector for coupling the adaptor with a monopolar modehand switch connector of the electrosurgical generator, and at least onebipolar mode hand switch connector for coupling the adaptor with abipolar mode hand switch connector of the electrosurgical device.

The invention is also directed to various embodiments of a bipolarelectrosurgical device. In one preferred embodiment, the devicecomprises a first electrode tip and a second electrode tip with theelectrode tips coupled to an impedance transformer provided with theelectrosurgical device, at least one fluid delivery passage beingconnectable to a fluid source, at least one fluid outlet opening influid communication with the at least one fluid delivery passage, theelectrode tips configured to paint along a tissue surface in thepresence of fluid from the fluid outlet opening as the tips are movedalong the tissue surface whereby the tissue surface can be coagulatedwithout cutting upon the application of radio frequency energy from theelectrodes simultaneously with fluid from the fluid outlet opening whilethe tips are coupled with the fluid adjacent the tissue surface andmoved along the tissue surface.

The invention is also directed to various embodiments of medical kits.In one preferred embodiment, the kit has an electrosurgical deviceconfigured to provide radio frequency power and a fluid to a tissuetreatment site, and a transformer. In various embodiments, theelectrosurgical device and transformer may be provided as separateconnectable components, or integrally as a single piece.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing one embodiment of a control system ofthe invention, and an electrosurgical device;

FIG. 2 is a schematic graph that describes a relationship between RFpower to tissue (P, in watts), flow rate of saline (Q, in cc/sec.), andtissue temperature (T, in ° C.) when heat conduction to adjacent tissueis considered;

FIG. 3 is schematic graph that describes a relationship between RF powerto tissue (P, in watts), flow rate of saline (Q, in cc/sec.), and tissuetemperature (T, in ° C.) when heat conduction to adjacent tissue isneglected;

FIG. 4 is a schematic graph that describes a relationship between RFpower to tissue (P, in watts), flow rate of saline (Q, in cc/sec.), andtissue temperature (T, in ° C.) when the heat required to warm thetissue to the peak temperature (T) is considered;

FIG. 5 is a graph that describes a relationship between percentagesaline boiling (%) and saline flow rate (Q, in cc/min) for an exemplaryRF generator output setting of 75 watts;

FIG. 6 is a schematic graph that describes a relationship between loadimpedance (Z, in ohms) and generator output power (P, in watts), for anexemplary RF generator output setting of 75 watts in a bipolar mode;

FIG. 7 is a schematic graph that describes a relationship between time(t, in seconds) and tissue impedance (Z, in ohms) after RF activation;

FIG. 8 is a schematic perspective view of a cannula which may be usedwith an electrosurgical device according to the present invention;

FIG. 9 is a schematic exploded perspective view of an assembly of anelectrosurgical device according to the present invention;

FIG. 10 is a schematic longitudinal cross-sectional side view of the tipand shaft of the device of FIG. 9 taken along line 10-10 of FIG. 12;

FIG. 11 is a schematic close-up longitudinal cross-sectional side viewof the tip portion of the device bounded by circle 45 shown in FIG. 10taken along line 10-10 of FIG. 12;

FIG. 12 is a schematic distal end view of the tip portion of the devicebounded by circle 45 shown in FIG. 10;

FIG. 13 is a schematic side view of the of the tip and shaft of thedevice of FIG. 9 with a fluid coupling to a tissue surface of tissue;

FIG. 14 is a schematic close-up side view of an alternative tip portion;

FIG. 15 is a schematic close-up cross-sectional side view of the tipportion of FIG. 14 taken along line 15-15 of FIG. 14;

FIG. 16 is a schematic close-up cross-sectional side view of the tipportion of FIG. 14 disposed in a tissue crevice;

FIG. 17 is a schematic graph that describes a relationship between time(t, in seconds) and changes in impedance (Z, in ohms) represented byimpedance spikes;

FIG. 18 is a schematic graph that describes a relationship betweenpercentage saline boiling (%) and impedance (Z, in ohms);

FIG. 19 is schematic close-up cross-sectional view of a sleeve takenalong line 19-19 of FIG. 15;

FIG. 20 is a schematic close-up perspective view of an alternative tipportion;

FIG. 21 is a schematic close-up cross-sectional side view of the tipportion of FIG. 20 taken along line 21-21 of FIG. 20;

FIG. 22 is a schematic close-up cross-sectional side view of the tipportion of FIG. 20 disposed in a tissue crevice;

FIG. 23 is a schematic close-up front perspective view of the electrodefor the tip portion of FIG. 20;

FIG. 24 is a schematic close-up rear perspective view of the electrodefor the tip portion of FIG. 20;

FIG. 25 is a schematic close up cross-sectional view of a porouselectrode with recesses;

FIG. 26 is schematic close up cross-sectional view of an electrode withsemi-circular recesses;

FIG. 27 is schematic close up cross-sectional view of an electrode withV-shaped recesses;

FIG. 28 is schematic close up cross-sectional view of an electrode withU-shaped recesses;

FIG. 29 is a schematic close-up perspective view of an alternative tipportion;

FIG. 30 is a schematic close-up cross-sectional side view of the tipportion of FIG. 29 taken along line 30-30 of FIG. 29;

FIG. 31 is a schematic close-up perspective view of an alternative tipportion;

FIG. 32 is a schematic close-up cross-sectional side view of the tipportion of FIG. 31 taken along line 32-32 of FIG. 31;

FIG. 33 is a schematic close-up perspective view of an alternative tipportion;

FIG. 34 is a schematic close-up cross-sectional side view of the tipportion of FIG. 33 taken along line 34-34 of FIG. 33;

FIG. 35 is a schematic close-up perspective view of an alternative tipportion;

FIG. 36 is a schematic close-up cross-sectional side view of the tipportion of FIG. 35 taken along line 36-36 of FIG. 35;

FIG. 37 is a schematic close up side view of an alternative cone shapeportion of an electrode;

FIG. 38 is a schematic close up side view of an alternative cone shapeportion of an electrode;

FIG. 39 is a schematic close up side view of an alternative cone shapeportion of an electrode;

FIG. 40 is a schematic close up side view of an alternative cone shapeportion of an electrode;

FIG. 41 is a schematic exploded perspective view of an assembly of analternative electrosurgical device according to the present invention;

FIG. 42 is a schematic close-up cross-sectional side view of the tipportions of FIG. 41 assembled with a fluid coupling to a tissue surfaceof tissue;

FIG. 43 is a schematic close-up cross-sectional side view of the tipportions of FIG. 41 assembled with an alternative fluid coupling to atissue surface of tissue;

FIG. 44 is a block diagram showing another embodiment of a controlsystem of the invention, and an electrosurgical device;

FIG. 45 is a block diagram of an electrical configuration for agenerator and a bipolar device without a hand switch;

FIG. 46 is a block diagram of an electrical configuration for agenerator and a monopolar device with a hand switch;

FIG. 47 is a block diagram of an electrical configuration for agenerator and a bipolar device with a hand switch and a transformer;

FIG. 48 is a block diagram of an electrical configuration for agenerator and a bipolar device without a handswitch and with atransformer;

FIG. 49 is a block diagram of an electrical configuration for agenerator, a bipolar device without a hand switch, and an adaptor with atransformer therebetween;

FIG. 50 is a block diagram of an electrical configuration for agenerator and a bipolar device with a hand switch;

FIG. 51A is a block diagram of an electrical configuration for agenerator, a bipolar device with a hand switch, and an adaptor with atransformer therebetween;

FIG. 51B is a block diagram of an electrical configuration for agenerator, a bipolar device with a hand switch, and an adaptor with atransformer therebetween;

FIG. 52 is a schematic perspective view of an alternativeelectrosurgical device according to the present invention;

FIG. 53 is a schematic perspective view of a handle portion of thedevice of FIG. 52 assembled with various components;

FIG. 54 is a schematic side view of a handle portion of the device ofFIG. 52 assembled with various components;

FIG. 55 is a schematic side view of a handle portion of the device ofFIG. 52 assembled with various components;

FIG. 56 is a schematic side view of a handle portion of the device ofFIG. 52 assembled with various components;

FIG. 57 is a schematic perspective view of an alternativeelectrosurgical device according to the present invention;

FIG. 58 is a schematic perspective view of a handle portion of thedevice of FIG. 57 assembled with various components; and

FIG. 59 is a schematic side view of a handle portion of the device ofFIG. 52 assembled with various components.

DETAILED DESCRIPTION

Throughout the description, like reference numerals and letters indicatecorresponding structure throughout the several views, and suchcorresponding structure need not be separately discussed. Furthermore,any particular feature(s) of a particular exemplary embodiment may beequally applied to any other exemplary embodiment(s) of thisspecification as suitable. In other words, features between the variousexemplary embodiments described herein are interchangeable as suitable,and not exclusive.

The invention provides devices, systems and methods that control tissuetemperature at a tissue treatment site during a medical procedure. Thisis particularly useful during surgical procedures upon tissues of thebody, where it is desirable to seal, coagulate and shrink tissue, toocclude lumens of blood vessels (e.g., arteries, veins), airways (e.g.,bronchi, bronchioles), bile ducts and lymphatic ducts.

The invention includes electrosurgical procedures, which preferablyutilize RF power and electrically conductive fluid, to treat tissue.Preferably, a desired tissue temperature range is achieved by adjustingparameters, such as fluid flow rate, to affect the temperature at thetissue/electrode interface.

In one embodiment, the invention provides a control device, the devicecomprising a flow rate controller that receives a signal indicatingpower applied to the system, and adjusts the flow rate of fluid from afluid source to the electrosurgical device. The invention also providesa control system comprising a flow rate controller, a measurement devicethat measures power applied to the system, and a pump that providesfluid at a selected flow rate.

The invention will be discussed generally with reference to FIG. 1,which shows a block diagram of one exemplary embodiment of a system ofthe invention. Preferably, an electrically conductive fluid 24 isprovided from a fluid source 1 through a fluid line 2 to a pump 3, whichhas an outlet fluid line 4 a that is connected as an input fluid line 4b to electrosurgical device 5. In a preferred embodiment, outlet fluidline 4 a and input fluid line 4 b are flexible and are made from apolymeric material, such as polyvinylchloride (PVC) or polyolefin (e.g.,polypropylene, polyethylene) and the conductive fluid comprises a salinesolution. More preferably, the saline comprises sterile, and even morepreferably, normal saline. Although the description herein willspecifically describe the use of saline as the fluid 24, otherelectrically conductive fluids, as well as non-conductive fluids, can beused in accordance with the invention.

For example, in addition to the conductive fluid comprising physiologicsaline (also known as “normal” saline, isotonic saline or 0.9% sodiumchloride (NaCl) solution), the conductive fluid may comprise hypertonicsaline solution, hypotonic saline solution, Ringers solution (aphysiologic solution of distilled water containing specified amounts ofsodium chloride, calcium chloride, and potassium chloride), lactatedRinger's solution (a crystalloid electrolyte sterile solution ofdistilled water containing specified amounts of calcium chloride,potassium chloride, sodium chloride, and sodium lactate), Locke-Ringer'ssolution (a buffered isotonic solution of distilled water containingspecified amounts of sodium chloride, potassium chloride, calciumchloride, sodium bicarbonate, magnesium chloride, and dextrose), or anyother electrolyte solution.

While a conductive fluid is preferred, as will become more apparent withfurther reading of this specification, fluid 24 may also comprise anelectrically non-conductive fluid. The use of a non-conductive fluid isless preferred than a conductive fluid, however, the use of anon-conductive fluid still provides certain advantages over the use of adry electrode including, for example, reduced occurrence of tissuesticking to the electrode of device 5 and cooling of the electrodeand/or tissue. Therefore, it is also within the scope of the inventionto include the use of a non-conducting fluid, such as, for example,deionized water.

Returning to FIG. 1, energy to heat tissue is provided from an energysource, such as an electrical generator 6 which preferably provides RFalternating current via a cable 7 to an energy source output measurementdevice, such as a power measurement device 8 that measures the RFalternating current electrical power. In one exemplary embodiment,preferably the power measurement device 8 does not turn the power off oron, or alter the power in any way. A power switch 15 connected togenerator 6 is preferably provided by the generator manufacturer and isused to turn generator 6 on and off. The power switch 15 can compriseany switch to turn the power on and off, and is commonly provided in theform of a footswitch or other easily operated switch, such as a switch15 a mounted on electrosurgical device 5. The power switch 15 or 15 amay also function as a manually activated device for increasing ordecreasing the power provided from device 5. Alternatively, internalcircuitry and other components of generator 6 may be used forautomatically increasing or decreasing the power provided from device 5.A cable 9 preferably provides RF power from power measurement device 8to electrosurgical device 5. Power, or any other energy source output,is preferably measured before it reaches electrosurgical device 5.

When capacitation and induction effects are negligibly small, from Ohm'slaw, power P, or the rate of energy delivery (e.g., joules/sec), may beexpressed by the product of current times voltage (i.e., I×V), thecurrent squared times resistance (i.e., I²×R), or the voltage squareddivided by the resistance (i.e., V²/R); where the current I may bemeasured in amperes, the voltage V may be measured in volts, theelectrical resistance R may be measured in ohms, and the power P may bemeasured in watts (joules/sec). Given that power P is a function ofcurrent I, voltage V, and resistance R as indicated above, it should beunderstood, that a change in power P is reflective of a change in atleast one of the input variables. Thus, one may alternatively measurechanges in such input variables themselves, rather than power Pdirectly, with such changes in the input variables mathematicallycorresponding to a changes in power P as indicated above.

Heating of the tissue is preferably performed by electrical resistanceheating. That is, the temperature of the tissue increases as a result ofelectric current flow through the tissue, with the electrical energybeing absorbed from the voltage and transformed into thermal energy(i.e., heat) via accelerated movement of ions as a function of thetissue's electrical resistance.

Referring again to FIG. 1, a flow rate controller 11 preferably includesa selection switch 12 that can be set to achieve desired levels ofpercentage fluid boiling (for example, 100%, 98%, 80% boiling).Preferably, flow rate controller 11 receives an input signal 10 frompower measurement device 3 and calculates an appropriate mathematicallypredetermined fluid flow rate based on percentage boiling indicated bythe selection switch 12. In a preferred embodiment, a fluid switch 13 isprovided so that the fluid system can be primed (e.g., air eliminated)before turning on generator 6. The output signal 16 of flow ratecontroller 11 is preferably sent to pump 3 motor to regulate the flowrate of fluid, and thereby provide an appropriate fluid flow rate whichcorresponds to the amount of power being delivered.

In one embodiment, flow rate controller 11 is configured and arranged tobe connected to a source of RF power (e.g., generator 6), and a sourceof fluid (e.g., fluid source 1), for example, a source of conductivefluid. The device of the invention receives information about the levelof RF power applied to electrosurgical device 5, and adjusts the flowrate of fluid 24 to electrosurgical device 5, thereby controllingtemperature at the tissue treatment site.

In another embodiment, elements of the system are physically includedtogether in one electronic enclosure. One such embodiment is shown byenclosure within the outline box 14 of FIG. 1. In the illustratedembodiment, pump 3, flow rate controller 11, and power measurementdevice 8 are enclosed within an enclosure, and these elements areconnected through electrical connections to allow signal 10 to pass frompower measurement device 8 to flow rate controller 11, and signal 16 topass from flow rate controller 11 to pump 3. Other elements of a systemcan also be included within one enclosure, depending upon such factorsas the desired application of the system, and the requirements of theuser.

Pump 3 can be any suitable pump to provide saline or other fluid at adesired flow rate. Preferably, pump 3 is a peristaltic pump. With arotary peristaltic pump, typically a fluid 24 is conveyed within theconfines of a flexible tube (e.g., 4 a) by waves of contraction placedexternally on the tube which are produced mechanically, typically byrotating rollers which intermittently squeeze the flexible tubingagainst a support with a linear peristaltic pump, typically a fluid 24is conveyed within the confines of a flexible tube by waves ofcontraction placed externally on the tube which are producedmechanically, typically by a series of compression fingers or pads whichsequentially squeeze the flexible tubing against a support. Peristalticpumps are generally preferred, as the electromechanical force mechanism(e.g., rollers driven by electric motor) does not make contact the fluid24, thus reducing the likelihood of inadvertent contamination.

Similar pumps can be used in connection with the invention, and theillustrated embodiments are exemplary only. The precise configuration ofpump 3 is not critical to the invention. For example, pump 3 may includeother types of infusion and withdrawal pumps. Furthermore, pump 3 maycomprise pumps which may be categorized as syringe pumps, piston pumps,rotary vane pumps (e.g., axial impeller, centrifugal impeller),cartridge pumps and diaphragm pumps. In some embodiments, pump 3 can besubstituted with any type of flow controller, such as a manual rollerclamp used in conjunction with an IV bag, or combined with the flowcontroller to allow the user to control the flow rate of conductivefluid to the device. Alternatively, a valve configuration can besubstituted for pump 3.

Fluid 24, such as conductive fluid, is preferably provided from anintravenous (IV) bag full of saline (e.g., fluid source 1) that flows bygravity. Fluid 24 may flow directly to electrosurgical device 5, orfirst to pump 3 located there between. Alternatively, fluid 24 from afluid source 1 such as an IV bag can be provided through an IV flowcontroller that may provide a desired flow rate by adjusting the crosssectional area of a flow orifice (e.g., lumen of the connective tubingwith the electrosurgical device 5) while sensing the flow rate with asensor such as an optical drop counter. Furthermore, fluid 24 from afluid source 1 such as an IV bag can be provided through a manually orautomatically activated device such as a flow controller, such as aroller clamp, which also adjusts the cross sectional area of a floworifice and may be adjusted manually by, for example, the user of thedevice in response to their visual observation (e.g., fluid boiling) atthe tissue treatment site or a pump.

Similar configurations of the system can be used in connection with theinvention, and the illustrated embodiments are exemplary only. Forexample, the fluid source 1, pump 3, generator 6, power measurementdevice 8 or flow rate controller 11, or any other components of thesystem not expressly recited above, may be present as a part of theelectrosurgical device 5. For example, fluid source 1 may be acompartment of the electrosurgical device 5 which contains fluid 24, asindicated at reference character 1 a . In another exemplary embodiment,the compartment may be detachably connected to electrosurgical device 5,such as a canister which may be attached via threaded engagement withdevice 5. In yet another embodiment, the compartment may be configuredto hold a pre-filled cartridge of fluid 24, rather than the fluiddirectly.

Also for example, with regards to alternatives for the generator 6, anenergy source, such as a direct current (DC) battery used in conjunctionwith inverter circuitry and a transformer to produce alternating currentat a particular frequency, may comprise a portion of the electrosurgicaldevice 5, as indicated at reference character 6 a. In one embodiment thebattery element of the energy source may comprise a rechargeablebattery. In yet another exemplary embodiment, the battery element may bedetachably connected to the electrosurgical device 5, such as forrecharging.

Use of the components of the system will now be described in furtherdetail. From the specification, it should be clear that any use of theterms “distal” and “proximal” are made in reference from the user of thedevice, and not the patient.

Flow rate controller 11 controls the rate of flow from the fluid source1. Preferably, the rate of fluid flow from fluid source 1 is based uponthe amount of RF power provided from generator 6 to electrosurgicaldevice 5. Referring to FIG. 2, there is illustrated a relationshipbetween the rate of fluid flow Q and the RF power P. More precisely, asshown in FIG. 2, the relationship between the rate of fluid flow Q andRF power P may be expressed as a direct, linear relationship. The flowrate Q of conductive fluid 24, such as saline, interacts with the RFpower P and various modes of heat transfer to transfer heat away fromthe target tissue, as described herein.

Throughout this disclosure, when the terms “boiling point of saline”,“vaporization point of saline”, and variations thereof are used, what isactually referenced for explanation purposes, is the boiling point ofthe water (i.e., 100° C.) in the saline solution given that thedifference between the boiling point of normal saline (about 100.16° C.)and the boiling point of water is negligible.

FIG. 2 shows the relationship between the flow rate of saline, RF powerto tissue, and regimes of boiling as detailed below. Based on a simple,one-dimensional, lumped parameter model of the heat transfer, the peaktissue temperature can be estimated, and once tissue temperature isestimated, it follows directly whether it is hot enough to boil saline.The total RF electrical power P that is converted into heat can bedefined as:P=ΔT/R+ρc _(p) Q ₁ ΔT+ρQ _(b) h _(v)   (1)where P=the total RF electrical power that is converted into heat.

Conduction. The first term [ΔT/R] in equation (1) is heat conducted toadjacent tissue, represented as 70 in FIG. 2, where:

-   -   ΔT=(T−T_(∞)) the difference in temperature (° C.) between the        peak tissue temperature (T) and the normal temperature (T_(∞))        of the body tissue; normal temperature of the body tissue is        generally 37° C.; and    -   R=Thermal resistance of surrounding tissue, the ratio of the        temperature difference to the heat flow (° C./watt).

This thermal resistance can be estimated from published data gathered inexperiments on human tissue (see for example, Phipps, J. H.,“Thermometry studies with bipolar diathermy during hysterectomy,”Gynaecological Endoscopy, 3:5-7 (1994)). As described by Phipps,Kleppinger bipolar forceps were used with an RF power of 50 watts, andthe peak tissue temperature reached 320° C. For example, using theenergy balance of equation (1), and assuming all the RF heat put intotissue is conducted away, then R can be estimated:R=ΔT/P=(320-37)/50=5.7≈6° C./watt

However, it is undesirable to allow the tissue temperature to reach 320°C., since tissue will become desiccated. At a temperature of 320° C.,the fluid contained in the tissue is typically boiled away, resulting inthe undesirable tissue effects described herein. Rather, it is preferredto keep the peak tissue temperature at no more than about 100° C. toinhibit desiccation of the tissue. Assuming that saline boils at about100° C., the first term in equation (1) (ΔT/R) is equal to(100−37)/6=10.5 watts. Thus, based on this example, the maximum amountof heat conducted to adjacent tissue without any significant risk oftissue desiccation is 10.5 watts.

Referring again to FIG. 2, RF power to tissue is represented on theX-axis as P (watts) and flow rate of saline (cc/min) is represented onthe Y-axis as Q. When the flow rate of saline equals zero (Q=0), thereis an “offset” RF power that shifts the origin of the sloped lines 76,78, and 80 to the right. This offset is the heat conducted to adjacenttissue. For example, using the calculation above for bipolar forceps,this offset RF power is about 10.5 watts. If the power is increasedabove this level with no saline flow, the peak tissue temperature canrise well above 100° C., resulting in tissue desiccation from theboiling off of water in the cells of the tissue.

Convection. The second term [ρc_(ρ)Q₁ΔT] in equation (1) is heat used towarm up the saline without boiling the saline, represented as 72 in FIG.2, where:

-   -   ρ=Density of the saline fluid that gets hot but does not boil        (approximately 1.0 gm/cm³);    -   c_(ρ)=Specific heat of the saline (approximately 4.1        watt-sec/gm-° C.);    -   Q₁=Flow rate of the saline that is heated (cm³/sec); and    -   ΔT=Temperature rise of the saline. Assuming that the saline is        heated to body temperature before it reaches the electrode, and        that the peak saline temperature is similar to the peak tissue        temperature, this is the same ΔT as for the conduction        calculation above.

The onset of boiling can be predicted using equation (1) with the lastterm on the right set to zero (no boiling), i.e. ρQ_(b)h_(v)=0, andsolving equation (1) for Q₁ leads to:Q ₁ =[P−ΔT/R]/ρc _(ρ) ΔT   (2)

This equation defines the line shown in FIG. 2 as the line of onset ofboiling 76.

Boiling. The third term [ρQ_(b)h_(v)] in equation (1) relates to heatthat goes into converting the water in liquid saline to water vapor, andis represented as 74 in FIG. 2, where:

-   -   Q_(b)=Flow rate of saline that boils (cm³/sec); and    -   h_(v)=Heat of vaporization of saline (approximately 2,000        watt-sec/gm).

A flow rate of only 1 cc/min will absorb a significant amount of heat ifit is completely boiled, or about ρQ_(b)h_(v)=(1) (1/60) (2,000)=33.3watts. The heat needed to warm this flow rate from body temperature to100° C. is much less, or ρc_(p)Q₁ΔT=(1) (4.1) (1/60) (100−37)=4.3 watts.In other words, the most significant factor contributing to heattransfer from a wet electrode device can be fractional boiling. Thepresent invention recognizes this fact and exploits it.

Fractional boiling can be described by equation (3) below:$\begin{matrix}{Q_{1} = \frac{\{ {P - {\Delta\quad{T/R}}} \}}{\{ {{\rho\quad c_{p}\Delta\quad T} + {\rho\quad h_{v}{Q_{b}/Q_{l}}}} \}}} & (3)\end{matrix}$

If the ratio of Q_(b)/Q₁ is 0.50 this is the 50% boiling line 78 shownin FIG. 2. If the ratio is 1.0 this is the 100% boiling line 80 shown inFIG. 2.

As indicated previously in the specification, use of a fluid to coupleenergy to tissue inhibits undesirable effects such as tissuedesiccation, electrode sticking, char formation and smoke production.Tissue desiccation, which occurs if the tissue temperature exceeds 100°C. and all the intracellular water boils away, is particularlyundesirable as it leaves the tissue extremely dry and much lesselectrically conductive.

As shown in FIG. 2, one control strategy or mechanism which can beemployed for the electrosurgical device 5 is to adjust the power P andflow rate Q such that the power P used at a corresponding flow rate Q isequal to or less than the power P required to boil 100% of the fluid,and does not exceed the power P required to boil 100% of the fluid. Thiscontrol strategy targets using the electrosurgical device 5 in theregions of FIG. 2 identified as T<100° C. and T=100° C., and includesthe 100% boiling line 80. That is, this control strategy targets notusing the electrosurgical device 5 only in the region of FIG. 2identified as T>>100° C.

Another control strategy that can be used for the electrosurgical device5 is to operate device 5 in the region T<100° C., but at high enoughtemperature to shrink tissue containing Type I collagen (e.g., walls ofblood vessels, bronchi, bile ducts, etc.), which shrinks when exposed toabout 85° C. for an exposure time of 0.01 seconds, or when exposed toabout 65° C. for an exposure time of 15 minutes. An exemplary targettemperature/time for tissue shrinkage is about 75° C. with an exposuretime of about 1 second. A determination of the high end of the scale(i.e., when the fluid reaches 100° C.) can be made by the phase changein the fluid from liquid to vapor. However, a determination at the lowend of the scale (e.g., when the fluid reaches, for example, 75° C. for1 second) requires a different mechanism as the temperature of the fluidis below the boiling temperature and no such phase change is apparent.

In order to determine when the fluid reaches a temperature that willfacilitate tissue shrinkage, for example 75° C., a thermochromicmaterial, such as a thermochromic dye (e.g., leuco dye), may be added tothe fluid. The dye can be formulated to provide a first predeterminedcolor to the fluid at temperatures below a threshold temperature, suchas 75° C., then, upon heating above 75° C., the dye provides a secondcolor, such as clear, thus turning the fluid clear (i.e., no color orreduction in color). This color change may be gradual, incremental, orinstant. Thus, a change in the color of the fluid, from a first color toa second color (or lack thereof) provides a visual indication to theuser of the electrosurgical device 5 as to when a threshold fluidtemperature below boiling has been achieved. Thermochromic dyes areavailable, for example, from Color Change Corporation, 1740 CortlandCourt, Unit A, Addison, Ill. 60101.

It is also noted that the above mechanism (i.e., a change in the colorof the fluid due to a dye) may also be used to detect when the fluidreaches a temperature which will facilitate tissue necrosis; thisgenerally varies from about 60° C. for an exposure time of 0.01 secondsand decreasing to about 45° C. for an exposure time of 15 minutes. Anexemplary target temperature/time for tissue necrosis is about 55° C.for an exposure time of about 1 second.

In order to reduce time, use of the electrosurgical device 5 in theregion T=100° C. of FIG. 2 is preferable to use of the electrosurgicaldevice 5 in the region T<100° C. Consequently, as shown in FIG. 2,another control strategy which may be employed for the electrosurgicaldevice 5 is to adjust the power P and flow rate Q such that the power Pused at a corresponding flow rate Q is equal to or more than the power Prequired to initiate boiling of the fluid, but still less than the powerP required to boil 100% of the fluid. This control strategy targetsusing the electrosurgical device 5 in the region of FIG. 2 identified asT=100° C., and includes the lines of the onset of boiling 76 and 100%boiling line 80. That is, this control strategy targets using theelectrosurgical device 5 on or between the lines of the onset of boiling76 and 100% boiling line 80, and not using the electrosurgical device 5in the regions of FIG. 2 identified as T<100° C. and T>>100° C.

For consistent tissue effect, it is desirable to control the saline flowrate so that it is always on a “line of constant % boiling” as, forexample, the line of the onset of boiling 76 or the 100% boiling line 80or any line of constant % boiling located in between (e.g., 50% boilingline 78) as shown in FIG. 2. Consequently, another control strategy thatcan be used for the electrosurgical device 5 is to adjust power P andflow rate Q such that the power P used at a corresponding flow rate Qtargets a line of constant % boiling.

It should be noted, from the preceding equations, that the slope of anyline of constant % boiling is known. For example, for the line of theonset of boiling 76, the slope of the line is given by (ρc_(ρ)ΔT), whilethe slope of the 100% boiling line 80 is given by 1/(ρc_(ρ)ΔT+ρρh_(v)).As for the 50% boiling line 78, for example, the slope is given by1/(ρc_(ρ)ΔT+ρh_(v)0.5).

If, upon application of the electrosurgical device 5 to the tissue,boiling of the fluid is not detected, such indicates that thetemperature is less than 100° C. as shown by the area T<100° C. of FIG.2, and the flow rate Q must be decreased to initiate boiling if thepower remains unchanged. The flow rate Q may be decreased until boilingof the fluid is first detected, at which time the line of the onset ofboiling 76 is transgressed and the point of transgression on the line 76is determined. From the determination of a point on the line of theonset of boiling 76 for a particular power P and flow rate Q, and theknown slope of the line 76 as outlined above (i.e., 1/ρc_(ρ)ΔT), it isalso possible to determine the heat conducted to adjacent tissue 70.

Conversely, if upon application of the electrosurgical device 5 to thetissue, boiling of the fluid is detected, such indicates that thetemperature is approximately equal to 100° C. as shown by the areaT=100° C. of FIG. 2, and the flow rate Q must be increased to reduceboiling until boiling stops, at which time the line of the onset ofboiling 76 is transgressed and the point of transgression on the line 76determined. As with above, from the determination of a point on the lineof the onset of boiling 76 for a particular power P and flow rate Q, andthe known slope of the line 76, it is also possible to determine theheat conducted to adjacent tissue 70.

With regards to the detection of boiling of the fluid, preferably suchis physically detected by the user (e.g., visually by the naked eye) inthe form of either bubbles or steam evolving from the fluid coupling atthe electrode/tissue interface. Alternatively, such a phase change(i.e., from liquid to vapor or vice-versa) may be measured by a sensorwhich preferably senses either an absolute change (e.g., existence ornon-existence of boiling with binary response such as yes or no) or achange in a physical quantity or intensity and converts the change intoa useful input signal for an information-gathering system. For example,the phase change associated with the onset of boiling may be detected bya pressure sensor, such as a pressure transducer, located on theelectrosurgical device 5. Alternatively, the phase change associatedwith the onset of boiling may be detected by a temperature sensor, suchas a thermistor or thermocouple, located on the electrosurgical device5, such as adjacent to the electrode. Also alternatively, the phasechange associated with the onset of boiling may be detected by a changein the electric properties of the fluid itself. For example, a change inthe electrical resistance of the fluid may be detected by an ohm meter;a change in the amperage may be measured by an amp meter; a change inthe voltage may be detected by a volt meter; and a change in the powermay be determined by a power meter.

Yet another control strategy which may be employed for theelectrosurgical device 5 is to eliminate the heat conduction term 70 ofequation (1) (i.e., ΔT/R). Since the amount of heat conducted away toadjacent tissue can be difficult to precisely predict, as it may vary,for example, by tissue type, it may be preferable, from a control pointof view, to assume the worst case situation of zero heat conduction, andprovide enough saline so that if necessary, all the RF power could beused to heat up and boil the saline, thus providing that the peak tissuetemperature will not go over 100° C. significantly. This is shown in theschematic graph of FIG. 3.

Stated another way, if the heat conducted to adjacent tissue 70 isoverestimated, the power P required to intersect the 100% boiling line80 will, in turn, be overestimated and the 100% boiling line 80 will betransgressed into the T>>100° C. region of FIG. 2, which is undesirableas established above. Thus, assuming the worse case situation of zeroheat conduction provides a “safety factor” to avoid transgressing the100% boiling line 80. Assuming heat conduction to adjacent tissue 70 tobe zero also provides the advantage of eliminating the only term fromequation (1) which is tissue dependent, i.e., depends on tissue type.Thus, provided ρ, c_(p), ΔT, and h_(v) are known as indicated above, theequation of the line for any line of constant % boiling is known. Thus,for example, the 98% boiling line, 80% boiling line, etc. can bedetermined in response to a corresponding input from selection switch12. In order to promote flexibility, it should be understood that theinput from the selection switch preferably may comprise any percentageof boiling. Preferably the percentage of boiling can be selected insingle percent increments (i.e., 100%, 99%, 98%, etc.).

Upon determination of the line of the onset of boiling 76, the 100%boiling line 80 or any line of constant % boiling there between, it isgenerally desirable to control the flow rate Q so that it is always on aparticular line of constant % boiling for consistent tissue effect. Insuch a situation, flow rate controller 11 will adjust the flow rate Q ofthe fluid 24 to reflect changes in power P provided by the generator 6,as discussed in greater detail below. For such a use flow ratecontroller 11 may be set in a line of constant boiling mode, upon whichthe % boiling is then correspondingly selected.

As indicated above, it is desirable to control the saline flow rate Q sothat it is always on a line of constant % boiling for consistent tissueeffect. However, the preferred line of constant % boiling may vary basedon the type of electrosurgical device 5. For example, if with use of thedevice 5, shunting through saline is not an issue, then it can bepreferable to operate close to or directly on, but not over the line ofthe onset of boiling, such as 76 a in FIG. 3. This preferably keepstissue as hot as possible without causing desiccation. Alternatively, ifwith use of the device 5 shunting of electrical energy through excesssaline is an issue, then it can be preferable to operate along a line ofconstant boiling, such as line 78 a in FIG. 3, the 50% line. This simpleproportional control will have the flow rate determined by equation (4),where K is the proportionality constant:Q ₁ =K×P   (4)

In essence, when power P goes up, the flow rate Q will beproportionately increased. Conversely, when power P goes down, the flowrate Q will be proportionately decreased.

The proportionality constant K is primarily dependent on the fraction ofsaline that boils, as shown in equation (5), which is equation (3)solved for K after eliminating P using equation (4), and neglecting theconduction term (ΔT/R): $\begin{matrix}{K = \frac{1}{\{ {{\rho\quad c_{p}\Delta\quad T} + {\rho\quad h_{v}{Q_{b}/Q_{l}}}} \}}} & (5)\end{matrix}$

Thus, the present invention provides a method of controlling boiling offluid, such as a conductive fluid, at the tissue/electrode interface. Ina preferred embodiment, this provides a method of treating tissuewithout use of tissue sensors, such as temperature or impedance sensors.Preferably, the invention can control boiling of conductive fluid at thetissue/electrode interface and thereby control tissue temperaturewithout the use of feedback loops.

In describing the control strategy of the present invention describedthus far, focus has been drawn to a steady state condition. However, theheat required to warm the tissue to the peak temperature (T) may beincorporated into equation (1) as follows:P=ΔT/R+ρc _(ρ) Q ₁ ΔT+ρQ _(b) h _(v) +ρc _(ρ) VΔT/Δt   (6)

where ρc_(ρ)VΔT/Δt represents the heat required to warm the tissue tothe peak temperature (T) 68 and where:

-   -   ρ=Density of the saline fluid that gets hot but does not boil        (approximately 1.0 gm/cm³);    -   c_(ρ)=Specific heat of the saline (approximately 4.1        watt-sec/gm-° C.);    -   V=Volume of treated tissue;    -   ΔT=(T−T_(∞)) the difference in temperature (° C.) between the        peak tissue temperature (T) and the normal temperature (T_(∞))        of the body tissue; normal temperature of the body tissue is        generally 37° C.; and    -   Δt=(t−t_(∞)) the difference in time to achieve peak tissue        temperature (T) and the normal temperature (T_(∞)) of the body        tissue (° C.).

The inclusion of the heat required to warm the tissue to the peaktemperature (T) in the control strategy is graphically represented at 68in FIG. 4. With respect to the control strategy, the effects of the heatrequired to warm the tissue to the peak temperature (T) 68 should betaken into account before flow rate Q adjustment being undertaken todetect the location of the line of onset of boiling 76. In other words,the flow rate Q should not be decreased in response to a lack of boilingbefore at least a quasi-steady state has been achieved as the locationof the line of onset of boiling 76 will continue to move during thetransitory period. Otherwise, if the flow rate Q is decreased during thetransitory period, it may be possible to decrease the flow Q to a pointpast the line of onset of boiling 76 and continue past the 100% boilingline 80 which is undesirable. In other words, as temperature (T) isapproached the heat 68 diminishes towards zero such that the lines ofconstant boiling shift to the left towards the Y-axis.

FIG. 5 is an exemplary graph of flow rate Q versus % boiling for asituation where the RF power P is 75 watts. The percent boiling % isrepresented on the X-axis, and the saline flow rate Q (cc/min) isrepresented on the Y-axis. According to this example, at 100 % boilingthe most desirable predetermined saline flow rate Q is 2 cc/min. Alsoaccording to this example, flow rate Q versus % boiling at the remainingpoints of the graft illustrates a non-linear relationship as follows:TABLE 1 % Boiling and Flow Rate Q (cc/min) at RF Power P of 75 watts  0%17.4 10% 9.8 20% 6.8 30% 5.2 40% 4.3 50% 3.6 60% 3.1 70% 2.7 80% 2.4 90%2.2 100%  2.0

Typical RF generators used in the field have a monopolar power selectorswitch to 300 watts of power, and on occasion some have been found to beselectable up to 400 watts of power. In conformance with the abovemethodology, at 0% boiling with a corresponding power of 300 watts, thecalculated flow rate Q is 69.7 cc/min and with a corresponding power of400 watts the calculated flow rate Q is 92.9 cc/min. Thus, when usedwith typical RF generators in the field, a fluid flow rate Q of about100 cc/min or less with the present invention is expected to suffice forthe vast majority of applications.

As discussed herein, RF power delivery to tissue can be unpredictableand vary with time, even though the generator has been “set” to a fixedwattage. The schematic graph of FIG. 6 shows the general trends of theoutput curve of a typical general-purpose generator, with the outputpower changing as load impedance Z changes. Load impedance Z (in ohms)is represented on the X-axis, and generator output power P (in watts) isrepresented on the Y-axis. In the illustrated embodiment, theelectrosurgical power (RF) is set to 75 watts in a bipolar mode. Asshown in the figure, the power will remain constant as it was set aslong as the impedance Z stays between two cut-offs, low and high, ofimpedance, that is, for example, between 50 ohms and 300 ohms in theillustrated embodiment. Below load impedance Z of 50 ohms, the power Pwill decrease, as shown by the low impedance ramp 28 a. Above loadimpedance Z of 300 ohms, the power P will decrease, as shown by the highimpedance ramp 28 b. This change in output is invisible to the user ofthe generator and not evident when the generator is in use, such as inan operating room.

FIG. 7 shows the general trend of how tissue impedance generally changeswith time for saline-enhanced electrosurgery. As tissue heats up, thetemperature coefficient of the tissue and saline in the cells is suchthat the tissue impedance decreases until a steady-state temperature isreached upon which time the impedance remains constant. Thus, as tissueheats up, the load impedance Z decreases, potentially approaching theimpedance Z cut-off of 50 ohms. If tissue is sufficiently heated, suchthat the low impedance cut-off is passed, the power P decreases alongthe lines of the low impedance ramp 28 a of FIG. 6.

Combining the effects shown in FIG. 6 and FIG. 7, it becomes clear thatwhen using a general-purpose generator set to a “fixed” power, theactual power delivered can change dramatically over time as tissue heatsup and impedance drops. Looking at FIG. 6, if the impedance Z drops from100 to 75 ohms over time, the power output would not change because thecurve is “flat” in that region of impedances. If, however, the impedanceZ drops from 75 to 30 ohms one would transgress the low impedancecut-off and “turn the corner” onto the low impedance ramp 28 a portionof the curve and the power output would decrease dramatically.

According to one exemplary embodiment of the invention, the controldevice, such as flow rate controller 11, receives a signal indicatingthe drop in actual power delivered to the tissue and adjusts the flowrate Q of saline to maintain the tissue/electrode interface at a desiredtemperature. In a preferred embodiment, the drop in actual power Pdelivered is sensed by the power measurement device 8 (shown in FIG. 1),and the flow rate Q of saline is decreased by flow rate controller 11(also shown in FIG. 1). Preferably, this reduction in saline flow rate Qallows the tissue temperature to stay as hot as possible withoutdesiccation. If the control device was not in operation and the flowrate Q allowed to remain higher, the tissue would be over-cooled at thelower power input. This would result in decreasing the temperature ofthe tissue at the treatment site and lead to longer treatment time.

Flow rate controller 11 of FIG. 1 can include a delay mechanism, such asa timer, to automatically keep the saline flow on for several secondsafter the RF is turned off to provide a post-coagulation cooling of thetissue or “quench,” which can increase the strength of the tissue seal.Flow rate controller 11 can also include a delay mechanism, such as atimer, to automatically turn on the saline flow several seconds beforethe RF is turned on to inhibit the possibility of undesirable effects astissue desiccation, electrode sticking, char formation and smokeproduction. Optionally, flow rate controller 11 can include a low levelflow standby mechanism, such as a valve, which continues the saline flowat a standby flow level (which prevents the flow rate from going to zerowhen the RF power is turned off) below the surgical flow levelordinarily encountered during use of the electrosurgical device 5.

An exemplary electrosurgical device of the present invention which maybe used in conjunction with the system of the present invention is shownat reference character 5 a in FIG. 9, and more particularly in FIGS.9-13. While various electrosurgical devices of the present invention aredescribed with reference to use with the remainder of the system of theinvention, it should be understood that the description of thecombination is for purposes of illustrating the remainder of the systemof the invention only. Consequently, it should be understood that theelectrosurgical devices of the present invention can be used alone, orin conjunction with the remainder of the system of the invention, orthat a wide variety of electrosurgical devices can be used in connectionwith the remainder of the system of the invention. The electrosurgicaldevices disclosed herein are preferably further configured for both openand minimally invasive surgery, such as laparoscopic surgery. Forlaparoscopic surgery, the devices are preferably configured to fitthrough either a 5 mm or 12 mm trocar cannula.

As shown in FIG. 8, electrosurgical device 5 a may be used inconjunction with a cannula as illustrated at reference character 19,during laparoscopic surgery such as, for example, a laparoscopiccholecystectomy. Cannula 19 comprises a proximal portion 19 a separatedfrom a distal portion 19 b by an elongated rigid shaft portion 19 c.Proximal portion 19 a of cannula 19 preferably comprises a head portion19 d connected to rigid shaft portion 19 c, preferably by threadedengagement. Most importantly, cannula 19 has a working channel 19 ewhich extends through head portion 19 d and shaft portion 19 c fromproximal portion 19 a to distal portion 19 b of cannula 19. In oneparticular embodiment, during insertion into cannula 19, electrosurgicaldevice 5 a is configured to enter the proximal end of working channel 19e, move along the channel 19 e distally, and then be extended from thedistal end of the working channel 19 e. In the same embodiment, duringretraction from cannula 19, electrosurgical device 5 a is configured toenter the distal end of working channel 19 e, move along the channel 19e proximally, and then be removed from the proximal end of workingchannel 19 e.

Referring back to FIG. 9, as shown electrosurgical device 5 a is amonopolar electrosurgical device. Electrosurgical device 5 a preferablyincludes a rigid, self-supporting, hollow shaft 17, a proximal handlecomprising mating handle portions 20 a, 20 b and a tip portion as shownby circle 45. Handle 20 a, 20 b is preferably made of a sterilizable,rigid, non-conductive material, such as a polymer (e.g., polycarbonate).As shown in FIGS. 10 and 11, tip portion 45 includes a contact elementpreferably comprising an electrode 25 which, as shown, comprises a solidball having a smooth, uninterrupted surface. Tip portion 45 alsocomprises a sleeve 82 having a uniform diameter along its longitudinallength, a spring 88 and a distal portion of shaft 17. As shown in FIG.10, the longitudinal axis 31 of the tip portion 45 may be configured atan angle A relative to the longitudinal axis 29 of the proximalremainder of shaft 17. Preferably, angle A is about 5 degrees to 90degrees, and more preferably, angle A is about 8 degrees to 45 degrees.

As shown in FIGS. 10 and 11, for electrosurgical device 5 a, electrode25 generally has a spherical shape with a corresponding sphericalsurface, a portion 42 of which is exposed to tissue 32 at the distal endof device 5 a. When electrode 25 is in the form of a sphere, the spheremay have any suitable diameter. Typically, the sphere has a diameter inthe range between and including about 1 mm to about 7 mm, although ithas been found that when a sphere is larger than about 4 mm or less thanabout 2 mm tissue treatment can be adversely effected (particularlytissue treatment time) due to an electrode surface that is respectivelyeither to large or to small. Thus, preferably the sphere has a diameterin the range between and including about 2.5 mm to about 3.5 mm, morepreferably, about 3 mm.

It is understood that shapes other than a sphere can be used for thecontact element. Examples of such shapes include oblong or elongatedshapes. However, as shown in FIGS. 10 and 11, preferably a distal endsurface of electrosurgical device 5 a provides a blunt, rounded surfacewhich is non-pointed and non-sharp as shown by electrode 25.

As shown in FIGS. 10 and 11, electrode 25, is preferably located in acavity 81 of a cylindrical sleeve 82 providing a receptacle forelectrode 25. Among other things, sleeve 82 guides movement of electrode25. Among other things, sleeve 82 also functions as a housing forretaining electrode 25.

Also as shown in FIG. 11, a portion 44 of electrode 25, is retainedwithin cavity 81 while another portion 43 extends distally through thefluid outlet opening provided by circular fluid exit hole 26. Also asshown, sleeve 82 is connected, preferably via welding with silversolder, to the distal end 53 of shaft 17. For device 5 a, electrode 25,sleeve 82 and shaft 17 preferably include, and more preferably are madeat least almost essentially of, an electrically conductive metal, whichis also preferably non-corrosive. A preferred material is stainlesssteel. Other suitable metals include titanium, gold, silver andplatinum. Shaft 17 preferably is stainless steel hypo-tubing.

As for cavity 81, the internal diameter of cavity 81 surroundingelectrode 25 is preferably slightly larger than the diameter of thesphere, typically by about 0.25 mm. This permits the sphere to freelyrotate within cavity 81. Consequently, cavity 81 of sleeve 82 alsopreferably has a diameter in the range of about 1 mm to about 7 mm.

As best shown in FIGS. 11 and 12, in order to retain electrode 25,within the cavity 81 of sleeve 82, preferably the fluid exit hole 26,which ultimately provides a fluid outlet opening, of cavity 81 at itsdistal end 83 comprises a distal pinched region 86 which is reduced to asize smaller than the diameter of electrode 25, to inhibit escape ofelectrode 25 from sleeve 82. More preferably, the fluid exit hole 26 hasa diameter smaller than the diameter of electrode 25.

As best shown in FIG. 12, fluid exit hole 26 preferably has a diametersmaller than the diameter of electrode 25, which can be accomplished byat least one crimp 84 located at the distal end 83 of sleeve 82 which isdirected towards the interior of sleeve 82 and distal to the portion 44of electrode 25 confined in cavity 81. Where one crimp 84 is employed,crimp 84 may comprise a single continuous circular rim pattern. In thismanner, the contact element portion extending distally through the fluidoutlet opening (i.e., electrode portion 43) provided by fluid exit hole26 has a complementary shape to the fluid outlet opening provided byfluid exit hole 26, here both circular.

As shown in FIG. 12, crimp 84 may have a discontinuous circular rimpattern where crimp 84 is interrupted by at least one rectangular holeslot 85 formed at the distal end 83 of sleeve 82. Thus, the fluid outletopening located at the distal end of the device 5 a may comprise a firstportion (e.g., the circular fluid exit hole portion 26) and a secondportion (e.g., the slot fluid exit hole portion 85). As shown in FIG.12, preferably, crimp 84 comprises at least four crimp sections forminga circular rim pattern separated by four discrete slots 85 radiallylocated there between at 90 degrees relative to one another and equallypositioned around the fluid outlet opening first portion. Slots 85 arepreferably used to provide a fluid outlet opening or exit adjacentelectrode 25, when electrode 25 is fully seated (as discussed below)and/or when electrode 25 is not in use (i.e., not electrically charged)to keep surface portion 42 of the electrode surface of electrode 25 wet.Preferably, slots 85 have a width in the range between and includingabout 0.1 mm to 1 mm, and more preferably about 0.2 mm to 0.3 mm. As forlength, slots 85 preferably have a length in the range between andincluding about 0.1 mm to 1 mm, and more preferably bout 0.4 mm to 0.6mm.

As shown in FIG. 12, the contact element portion extending distallythrough the fluid outlet opening (i.e., electrode portion 43) extendsdistally through the fluid outlet opening first portion (e.g., thecircular fluid exit hole portion 26) and does not extend distallythrough the fluid outlet opening second portion (e.g., the slot fluidexit hole portion 85). In this manner an edge 91 of slot 85 remainsexposed to tissue 32 to provide a tissue separating edge as discussedbelow.

It should be understood that the particular geometry of fluid outletopening provided by the fluid exit hole located at the distal end ofdevice 5 a to the electrode is not critical to the invention, and allthat is required is the presence of a fluid exit hole which providesfluid 24 as required. For example, fluid exit hole 26 may have an ovalshape while electrode 25 has a different shape, such as a round shape.

As shown in FIG. 12, in addition to slot 85 providing a fluid exit, atleast one edge 91 of slot 85 may provide a tissue separating edgeadjacent a blunt surface (e.g., surface portion 42 of electrode 25)which may be used for blunt dissection when the electrosurgical device 5a is manipulated, particularly by rotating (e.g., twirling), abrading orimpacting. When edge 91 is used in such regard, it is preferred that theedge comprise a sharp edge with a sharp angle which has not been roundedby, for example, a fillet.

Turning to the proximal end of the tip (comprising electrode 25, spring88 and sleeve 82) of the device 5 a, as shown in FIG. 11, preferably theportion of sleeve 82 proximal to electrode 25, also has a proximalpinched region 87 which retains electrode 25 in the cavity 81 of sleeve82 and inhibits escape of electrode 25 from the cavity 81 of sleeve 82,such as a diameter smaller than the diameter of electrode 25.

While distal pinched region 86 and proximal pinched region 87 may beused solely to support electrode 25, in its position of use, theelectrode may be further supported by a compression spring 88 as shownin FIG. 11. The use of spring 88 is preferred to provide a variablelength support within the working length of the spring 88 for overcomingmanufacturing tolerances (e.g., length) between the fixed supports(i.e., pinched regions 86 and 87) of sleeve 82. As for maintainingproper location of the spring 88, sleeve 82 also comprises a lumen 89 asshown in FIG. 11, which, in addition to providing a direct passage forfluid, provides a guide tube for spring 88. Furthermore, the surfaceportion 60 of electrode 25, which contacts spring 88 may have a flatsurface rather than a curvilinear surface to better seat the springagainst electrode 25.

In addition to the above, spring 88 provides a multitude of functionsand advantages. For example, the configuration of the distal pinchedregion 86, proximal pinched region 87 and spring 88 offers the abilityto move electrode 25 distally and proximally within sleeve 82. As shownin FIG. 11, spring 88 is located proximal to electrode 25 between afirst load bearing surface comprising the electrode surface 60 and asecond load bearing surface comprising the distal end 53 of shaft 17. Inthis manner, spring 88 can be configured to provide a decompressionforce to seat electrode 25 against the distal pinched region 86, in thiscase the perimeter edge 92 of crimp 84, prior to use of electrosurgicaldevice 5 a.

Conversely, upon application of electrode 25 against surface 22 oftissue 32 with sufficient force to overcome the compression force of thespring 88, spring 88 compresses and electrode 25 retracts proximallyaway from distal pinched region 86, in this case perimeter edge 92 ofcrimp 84, changing the position thereof. In the above manner, thecontact element comprising electrode 25 is retractable into the cavity81 of the housing provided by sleeve 82 upon the application of aproximally directed force against surface 42 of the portion 43 ofelectrode 25 extending distally beyond the distal opening 26 located atthe distal end 83 of the housing and spring 88 functions as a retractionbiasing member.

By making electrode 25 positionable in the above manner via spring 88,electrosurgical device 5 a can be provided with a damper mechanism whichdampens the force of electrode 25 on tissue 32 being treated.

Furthermore, electrode 25 which can be positioned as outlined above cancomprise a fluid flow rate adjustment mechanism which incrementallyincreases the area of fluid exit hole 26 and the corresponding fluidflow rate in response to the incremental proximal retraction ofelectrode 25. In such an instance, electrode 25 functions as a valve byregulating flow of fluid 24 through fluid exit hole 26.

In various embodiments, spring 88 may be used in conjunction with thedistal pinched region 86 (e.g., crimp 84 comprising a single continuouscircular pattern) to provide a fluid seal between electrode 25 and thedistal pinched region 86 which stops fluid flow from the electrosurgicaldevice 5 a. In this manner, the electrosurgical device 5 a may be usedto provide both a wet electrode and dry electrode (i.e., when the fluidflow is on and off, respectively) with the energy and fluid providedsequentially as opposed to simultaneously.

Furthermore, in various embodiments of electrosurgical device 5 a, anelectrode 25 which can be positioned as outlined above can include adeclogging mechanism. Such a mechanism can retract to provide access forunclogging fluid exit holes (e.g., 26 and 85), which may become flowrestricted as a result of loose debris (e.g., tissue, blood, coagula)becoming lodged therein. For example, when a biasing force, such as froma handheld cleaning device (e.g., brush) or from pushing the distal tipagainst a hard surface such as a retractor, is applied to surface 42 ofelectrode 25 which overcomes the compression force of the spring 88causing the spring 88 to compress and electrode 25 to retract, the tipof the handheld cleaning device may by extended into the fluid exit hole26 for cleaning the fluid exit hole 26, perimeter edge 92, slot 85 andedge 91. Stated another way, electrode 25, which can be positioned asoutlined, provides a methodology for declogging a fluid exit hole byincreasing the cross-sectional area of the fluid exit hole to provideaccess thereto.

Additionally, in various embodiments of device 5 a, spring 88 comprisesan electrical conductor, particularly when electrode 25, is retracted toa non-contact position (i.e., not in contact) with sleeve 82.

In other embodiments, proximal pinched region 87 may comprise one ormore crimps similar to distal pinched region 86, such that electrode 25is retained in sleeve 82 both distally and proximally by the crimps.Also, in other embodiments, sleeve 82 may be disposed within shaft 17rather than being connected to the distal end 53 of shaft 17. Also, instill other embodiments, sleeve 82 may be formed unitarily (i.e., as asingle piece or unit) with shaft 17 as a unitary piece.

As best shown in FIGS. 10 and 11, electrode 25 is retained in sleeve 82with a portion 43 of electrode 25 extending distally beyond distal end83 of sleeve 82. As shown, preferably the surface 42 of this exposedportion 43 of electrode 25 is blunt and does not have any sharp corners.Also, the portion 43 of electrode 25 which extends distally beyond thedistal end 83 of sleeve 82 is controlled by the shape of the fluid exithole 26 in sleeve 82 in relation to the shape of electrode 25. In otherwords, the portion 43 of electrode 25 that extends distally beyonddistal end 83 of sleeve 82 is controlled by the contact of the electrodesurface with the edge 92.

In locations where shaft 17 and sleeve 82 are electrically conductive(for device 5 a, preferably shaft 17 and sleeve 82 are completelyelectrically conductive and do not comprise non-conductive portions) anelectrical insulator 90 (i.e., comprising non-conductive or insulatingmaterial) preferably surrounds shaft 17 and sleeve 82 alongsubstantially its entire exposed length (e.g., the portion outside theconfines of the handle 20), terminating a short distance (e.g., at theproximal onset of crimp 84 or less than about 3 mm) from distal end 83of sleeve 82. Insulator 90 preferably comprises a shrink wrap polymertubing.

As with the other electrosurgical devices described within, a inputfluid line 4 b and a power source, preferably comprising generator 6preferably providing RF power via cable 9, are preferably fluidly andelectrically coupled, respectively, to the tip portion 45 of theelectrosurgical device 5 a.

As indicated above, device 5 a comprises a monopolar device. Forelectrosurgical device 5 a, electrode 25 provides an active electrode,while a ground pad dispersive electrode 125 (shown in FIG. 45) locatedon the patient, typically on the back or other suitable anatomicallocation, provides a return electrode. Preferably, both electrodes areelectrically coupled to generator 6 to form an isolated electricalcircuit. Preferably the active electrode is coupled to generator 6 via awire conductor from insulated wire cable 9 to the outer surface 18 ofshaft 17 within the confines of handle 20 a, 20 b, typically through aswitch such as 15 a.

Switch 15 a preferably comprises a dome switch having two electricalcontacts. The contacts preferably comprise upper and lower contactsdisposed on a platform in overlying relationship. Preferably the uppercontact comprises a dome shaped configuration overlying and spaced fromthe lower contact which is flat. Preferably the contacts are spaced fromone another by virtue of the domed configuration of the upper contactwhen the switch 15 a is in an undepressed position, thus creating anopen control circuit relative to switch 15 a. However, when the uppercontact is pressed into a depressed position, the upper contact comesinto contact with the lower contact thus closing the hand switch controlcircuit. The presence of the closed control circuit is then sensed bygenerator 6 which then provides power to the electrode 25.

When a depression force is removed from the upper contact, the contactreturns to its undepressed domed position as a result of its resiliencyor elastic memory, thus returning switch 15 a to its undepressedposition and reopening the hand control circuit. The presence of theopen control circuit is then sensed by the generator which then stopsproviding power to electrode 25.

In some embodiments, shaft 17 may be made of an electricalnon-conducting material except for a portion at its distal end 53 thatcomes in contact with sleeve 82. This portion of shaft 17 that contactssleeve 82 should be electrically conducting. In this embodiment, thewire conductor from insulated wire cable 9 extends to this electricallyconducting portion of shaft 17. In still other embodiments, shaft 17 maycompletely comprise a non-conducting material as where the wireconductor from insulated wire cable 9 extends directly to sleeve 32.

With respect to the fluid coupling, fluid 24 from the fluid source 1preferably is communicated from fluid source 1 through a flexible,polyvinylchloride (PVC) outlet fluid line 4 a to a flexible,polyvinylchloride (PVC) inlet fluid line 4 b connected toelectrosurgical device 5 a. Outlet fluid line 4 a and inlet fluid line 4b are preferably connected via a male and female mechanical fastenerconfiguration; a preferred such connection is a Luer-Lok® connectionfrom Becton, Dickinson and Company. The lumen of the inlet line is thenpreferably interference fit over the outside diameter of shaft 17 toprovide a press fit seal there between. An adhesive may be used therebetween to strengthen the seal. Fluid 24 is then communicated down lumen23 of shaft 17 through lumen 89 and cavity 81 of sleeve 82 where it isexpelled from around and on the exposed surface 42 of electrode 25. Thisprovides a wet electrode for performing electrosurgery.

As shown in FIG. 13, during use of electrosurgical device 5 a, typicallya fluid coupling 30 preferably comprising a discrete, localized web andmore preferably comprising a triangular shaped web or bead portionproviding a film of fluid 24 is provided between surface 22 of tissue 32and electrode 25. When the user of electrosurgical device 5 a placeselectrode 25 at a tissue treatment site and moves electrode 25 acrossthe surface 22 of the tissue 32, fluid 24 is expelled around and onsurface 42 of electrode 25 at the distal end 83 of sleeve 82 and ontothe surface 22 of the tissue 32 via coupling 30. The fluid 24, inaddition to providing an electrical coupling between electrosurgicaldevice 5 a and tissue 32, lubricates surface 22 of tissue 32 andfacilitates the movement of electrode 25 across surface 22 of tissue 32.During movement of electrode 25, electrode 25 typically slides acrosssurface 22 of tissue 32, but also may rotate as electrode 25 movesacross surface 22 of tissue 32. Typically the user of theelectrosurgical device 5 a slides the electrode across surface 22 oftissue 32 back and forth with a painting motion while using fluid 24 as,among other things, a lubricating coating. Preferably the thickness ofthe fluid 24 between the distal end surface of electrode 25 and surface22 of tissue 32 at the outer edge of the coupling 30 is in the rangebetween and including about 0.05 mm to 1.5 mm, more preferably in therange between and including about 0.1 mm to 0.3 mm. Also preferably, incertain embodiments, the distal end tip of electrode 25 contacts surface22 of tissue 32 without any fluid 24 in between.

Another exemplary electrosurgical device is shown at reference character5 b in FIGS. 14-16. In this embodiment, electrical insulator 90preferably terminates proximally to sleeve 82 where sleeve 82 isconnected to the distal end 53 of shaft 17. In certain embodiments wheresleeve 82 is formed unitary shaft 17, electrical insulator 90 preferablyterminates proximally to proximal pinched region 87. In this manner, inaddition to the spherical surface portion 42 of electrode 25 and thenarrowing surface portion 41, here conical, of sleeve 82 being used fortreating tissue 32 when exposed thereto, a cylindrical surface 40 of acylindrical portion 39 of sleeve 82 and a broadening surface portion 47of broadening portion 54, here both conical, of sleeve 82 also functionas electrode surfaces for treating tissue. Thus, the electrode exposedto tissue 32 now comprises a cylindrical surface portion 40 and abroadening surface portion 47 in addition to the spherical surfaceportion 42 and the narrowing surface portion 41, with the cylindricalsurface portion 40 substantially increasing the surface area of theelectrode. As a result, electrode 25 has surfaces which are parallel andperpendicular to the longitudinal axis 31 of tip portion 45, and moreparticularly, sleeve 82 of electrosurgical device 5 b. In the abovemanner, front end use (e.g., surfaces 41 and 42), sideways use (e.g.,surface 40 and 47), or oblique use (e.g., surfaces 40, 41 and 42) ofelectrosurgical device 5 b is facilitated.

In the above manner, tip portion 45 now includes a first tissue treatingsurface (e.g., distal end spherical surface 42) and a second tissuetreating surface (e.g., side surface 40). As discussed above, preferablythe first tissue treating surface is configured for blunt dissectionwhile the second tissue treating surface is configured for coagulation.Additionally, tip portion 45 also has a third tissue treating surface(e.g., surface 41) located between the first tissue treating surface(e.g., surface 42) and a second tissue treating surface (e.g., surface40). Furthermore, tip portion 45 also has a fourth tissue treatingsurface (e.g., surface 47) located proximal and adjacent to surface 40.

With device 5 a, when electrode 25 is placed directly in contact withsurface 22 of tissue 32, tissue 32 may occlude fluid flow from fluidexit holes 26, 85 located at the distal end of device 5 a. Consequently,for device 5 b fluid exit holes 93, 94 may be located in the cylindricalside portion 39 of sleeve 82, either proximal or adjacent to electrode25, and either in addition to or as an alternative to fluid exit holes26, 85.

As shown in FIGS. 14 and 15, at least one fluid exit hole 93 ispreferably formed in the cylindrical longitudinal side surface 40 andthrough the wall of side portion 39 of sleeve 82 adjacent to electrode25 when electrode 25 is fully seated. Furthermore, preferably at leastone fluid exit hole 94 is formed in the cylindrical side portion 39 ofsleeve 82 proximal to electrode 25 when electrode 25 is fully seated.

Preferably, holes 93, 94 each has more than one hole which are equallyspaced radially in a circular pattern around the longitudinal axis 31 oftip portion 45, and more particularly sleeve 82. More preferably, holes93, 94 each comprise four discrete holes equally spaced 90 degreesaround the cylindrical side portion 39 of sleeve 82. Preferably holes93, 94 have a diameter in the range between and including about 0.1 mmto 1.0 mm, and more preferably have a length in the range between andincluding about 0.2 mm to 0.6 mm.

Electrode 25, which can be positioned as outlined above, can comprisenot only a valve for regulating fluid flow from the fluid exit holes,such as fluid exit hole 26, but also comprise a valve which, whileopening one fluid flow exit, simultaneously closes another fluid flowexit. For example, as electrode 25 retracts proximally, fluid exit hole26 is opened while fluid exit hole 93 is closed. Stated another way, anelectrode 25 which can be positioned as outlined above can provide amechanism for altering the size and/or location of the fluid exit holesduring use of electrosurgical device 5 b which may be necessary, forexample, to direct fluid to a particular tissue location or balancefluid flow among the fluid exit outlets.

Thus, as shown in FIGS. 14 and 15, surfaces 40, 41 and 47 of sleeve 82,and surface 42 of electrode 25 are all active electrode surfaces and canprovide electrical energy to tissue 32. Portions of this combinedelectrode surface can be wet by fluid flow from holes 26, 94 or 93, aswell as from the hole slots 85 in crimp 84 adjacent electrode 25.

The holes 94, 93 in the cylindrical sleeve 82 of the overall electrodesurface are intended to assure that fluid 24 is provided to the smooth,less rough, atraumatic sides of the electrode that may be predominatelyused for tissue coagulation and hemostasis (e.g., surfaces 40 and 47)rather than blunt dissection (e.g., surfaces 41 and 42). The most distalportion of the device may have a more rough, but also wetted, electrodesurface that can blunt dissect as well as coagulate tissue.

The electrode configuration shown in FIGS. 14 and 15 is particularlyuseful to a surgeon performing a liver resection. Once the outer capsuleof the liver is scored with a dry bovie blade along the planned line ofresection the distal tip of tip portion 45 is painted back and forthalong the line, resulting in coagulation of the liver parenchyma beneaththe scored capsule. As the tissue is coagulated under and around theelectrode surfaces 40, 41 and 42, the electrode is used to blunt dissectinto the coagulated parenchyma, with edge 91 of slots 85 around crimp 84providing roughness elements that aid in disrupting the tissue 32 andenabling the parting of tissue 32.

As shown in FIG. 16, the device 5 b can be used in a crevice 97 oftissue 32 to blunt dissect tissue 32 and coagulate it at the same time.Blunt dissection is preferred over sharp dissection, such as with ablade or scissors, since blunt dissection is less likely to tear ordamage the larger blood vessels or other vessels. Once identified byblunt dissection, very large vessels can be safely clipped, tied withsuture or sealed with some other device. If the larger vessels are notthus first “skeletonized” without being damaged by blunt dissection,they may bleed profusely and require much more time to stop thebleeding. The device can also be used to coagulate first withoutsimultaneous blunt dissection, and then blunt dissect in a separatestep.

This technique can also be used on other parenchymal organs such as thepancreas, the kidney, and the lung. In addition, it may also be usefulon muscle tissue and subcutaneous fat. Its use can also extend to benigntumors, cysts or other tissue masses found in the urological orgynecological areas. It would also enable the removal of highlyvascularized tumors such as hemangiomas.

In FIG. 16 the zone 99 identifies the part of the electrode that has theability to blunt dissect and coagulate, and the zone 98 identifies thepart that is intended primarily for coagulation and hemostasis. The line100 indicates the depth of the zone of tissue that is coagulated,typically from 3 mm to 5 mm deep.

For the devices disclosed herein, the presence of various fractions ofboiling can be visually estimated by the naked eye, or by detectingchanges in electrical impedance. FIG. 17 shows a graph of electricalimpedance Z versus time t. The impedance spikes 101 shown in FIG. 17occur at a frequency of about 1 cycle per second and with an amplitudethat is on the same order as the baseline impedance. This frequency isshown in FIG. 17 as the interval 102 between successive impedancespikes. Impedance is directly measurable by dividing the voltage by thecurrent as previously described. The use of electrical impedance todetect the onset of tissue dessication when impedance rises dramaticallyas a result of being heated to the point of smoking and charring, butnot to detect the presence of boiling, is described above.

Shown in FIG. 18 is the qualitative nature of the boiling as the %boiling increases, indicated by the small figures for each of fiveexemplary “regimes” of boiling. In each small figure a portion of thetip of the tip portion 45 of device 5 a is shown in close proximity totissue 32. As boiling begins in regime 104, there are few small bubbles37 of vapor in the conductive fluid 24, here saline, of coupling 30. Asthe percentage of boiling increases at regime 106 there are a largernumber of small bubbles 37. As the percentage boiling increases furtherat regime 107, the bubbles 37 become much larger. At even higherpercentage boiling at regime 108 intermittent threads of saline form andare quickly boiled off. Finally, at the highest level of regime 109,drops 36 of saline are instantly boiled upon contacting the hot surface22 of tissue 32 and arcing occurs from the metal to tissue 32.

Returning to FIGS. 14 and 15, fluid outlet openings are provided bysubstantially linear through holes 93, 94 which provide conductive fluid24 to the treatment site. However, in an alternative embodiment, asshown in FIG. 19, fluid outlet openings in sleeve 82 may be provided byholes in the form of tortuous and interconnected pathways 59, which areformed in a material pervious to the passage of fluid 24, therethrough,such as a porous material. The discrete, linear through holes 93, 94 maybe either supplemented with or replaced by a plurality of tortuous,interconnected pathways 59 formed in the porous material which, amongother things, provides porous surfaces 40, 41 and 47 to more evenlydistribute fluid flow and provide the conductive fluid 24 to tissue 32at the treatment site. According to the invention, all or a portion ofsleeve 82 may comprise a material pervious to the passage of fluid 24therethrough as disclosed herein.

In certain embodiments, the contact element, here electrode 25 may alsocomprise a material pervious to the passage of fluid 24, therethrough,such as a porous material (e.g., metal, polymer or ceramic) to providethe tortuous pathways 59. In these embodiments, the porous structure ofelectrode 25 allows fluid 24 to not only pass around electrode 25 on theouter porous surface 42 to be expelled, but also allows fluid 24 to passthrough electrode 25, to be expelled. According to the invention, all ora portion of the electrodes or any particular electrodes for treatingtissue 32 may comprise a material pervious to the passage of fluid 24therethrough as disclosed herein.

Where the contact element and sleeve provide electrodes for treatingtissue and compromise a porous material, preferably the porous materialfurther comprises porous metal. Porous sintered metal is available inmany materials (such as, for example, 316L stainless steel, titanium,Ni-Chrome) and shapes (such as cylinders, discs, plugs) from companiessuch as Porvair, located in Henderson, N.C.

While the electrode provided by contact element and/or sleeve preferablycomprises an electrically conductive material such as metal, anon-electrically conductive porous contact element and/or sleeve, suchas porous polymers and ceramics, can be used to replace an electricallyconductive contact element and/or sleeve. While the porous polymers andceramics are generally non-conductive, they may also be used to conductthe RF energy through the porous polymer and ceramic thickness andporous surface to the tissue to be treated by virtue of conductive fluid24 contained within the plurality of interconnected tortuous pathways59.

Preferably the porous material provides for the wicking (i.e., drawingin of fluid by capillary action or capillarity) of the fluid 24 into thepores of the porous material. In order to promote wicking of the fluid24 into the pores of the porous material, preferably the porousmaterial, and in particular the surface of the tortuous pathways, ishydrophilic. The porous material may be hydrophilic with or without posttreating (e.g., plasma surface treatment such as hypercleaning, etchingor micro-roughening, plasma surface modification of the molecularstructure, surface chemical activation or crosslinking), or madehydrophilic by a coating provided thereto, such as a surfactant.

Though not preferable, it is not necessary that fluid coupling 30 offluid 24 be present in between the metal electrode surfaces (e.g., 40,41, 42) and tissue 32 at all locations of tissue treatment and there maybe points of direct tissue contact by the electrode surfaces without anyfluid coupling 30 therebetween. In such an instance, the convectivecooling of the metal electrode by flowing saline is often sufficient tokeep the metal electrode and tissue contacting the metal electrode at orbelow a temperature of 100° C. In other words, heat may be also firstdissipated from tissue 32 to the electrodes by conduction, thendissipated from the electrodes to the fluid 24 by convection.

Preferably the relationship between the material for electrodesparticularly their surfaces (e.g., 40, 41, 42, 47), and fluid 24throughout the various embodiments should be such that the fluid 24 wetsthe surface of the electrodes to form a continuous thin film coatingthereon (for example, see FIG. 21) and does not form isolated rivuletsor circular beads (e.g., with a contact angle, θ greater than 90degrees) which freely run off the surface of the electrode. Contactangle, θ, is a quantitative measure of the wetting of a solid by aliquid. It is defined geometrically as the angle formed by a liquid atthe three phase boundary where a liquid, gas and solid intersect. Interms of the thermodynamics of the materials involved, contact angle θinvolves the interfacial free energies between the three phases given bythe equation γ_(LV) cos θ=γ_(SV) −γ _(SL) where γ_(LV), γ_(SV) andγ_(SL) refer to the interfacial energies of the liquid/vapor,solid/vapor and solid/liquid interfaces, respectively. If the contactangle θ is less than 90 degrees the liquid is said to wet the solid. Ifthe contact angle is greater than 90 degrees the liquid is non-wetting.A zero contact angle θ represents complete wetting. Thus, preferably thecontact angle is less than 90 degrees.

For clarification, while it is known that the contact angle θ may bedefined by the preceding equation, in reality, contact angle θ isdetermined by various models, to an approximation. According to thepublication entitled “Surface Energy Calculations” (dated Sep. 13, 2001)from First Ten Angstroms (465 Dinwiddie Street, Portsmouth, Va. 23704),there are five models which are widely used to approximate contact angleθ and a number of others which have small followings. The fivepredominate models and their synonyms are: (1) Zisman critical wettingtension; (2) Girifalco, Good, Fowkes, Young combining rule; (3) Owens,Wendt geometric mean; (4) Wu harmonic mean; and (5) Lewis acid/basetheory. Also according to the First Ten Angstroms publication, forwell-known, well characterized surfaces, there can be a 25% differencein the answers provided for the contact angle θ by the models. Also forclarification, any one of the five predominate models above whichcalculates a contact angle θ within a particular range of contact anglesθ or the contact angle 74 required of a particular embodiment of theinvention should be considered as fulfilling the requirements of theembodiment, even if the remaining four models calculate a contact angleθ which does not fulfill the requirements of the embodiment.

The effects of gravity and surface tension tend to wick the fluid 24,here saline, around the circumference of the cylindrical sleeve 82 topreferably cover the entire active electrode surface. More specifically,the effects of gravity and surface tension on fluid 24 which is locatedon the electrode surfaces may be modeled by the Bond number N_(BO). Bondnumber N_(BO) measures the relationship of gravitational forces tosurface tension forces and may be expressed as:N _(BO) =ρL ² g/σ  (7)where:

-   -   ρ=Density of the saline fluid (approximately 1.0 gm/cm³);    -   L=Droplet diameter (cm);    -   g=Gravitational acceleration (980 cm/s²); and    -   ν=Surface tension (approximately 72.8 dynes/cm @20° C.)

For a Bond number N_(BO)=1, the droplet diameter is equal to about 0.273cm or about 2.7 mm, which is in the same order of magnitude as thepreferred size of the electrode. For the purposes of the presentinvention, preferably Bond number N_(BO) for a droplet of fluid 24 on asurface of electrode 25 is preferably less than 1.

Another tip portion of an exemplary electrosurgical device 5 c of thepresent invention which may be used in conjunction with the system ofthe present invention is shown at reference character 45 in FIGS. 20-24.As best shown in FIGS. 20 and 21, the separate sleeve 82 of embodiments5 a and 5 b has been eliminated from tip portion 45 of device 5 e.Consequently, the contact element, still preferably comprising anelectrode 25, is assembled directly with the shaft 17. Electrode 25 ispreferably assembled (e.g., mechanically connected via press fit,mechanical connector, threaded, welded, adhesively bonded) adjacent thedistal end 53 of shaft 17. In certain embodiments, electrode 25preferably is detachably assembled to the shaft 17 such that it may beremoved from the shaft 17, preferably manually by human hand, so thatthe shaft 17 may be used with multiple different contactelements/electrodes, or the shaft 17 may be reuseable and used withdisposable contact elements/electrodes.

As shown in FIGS. 20-24, electrode 25 preferably comprises an enlargedhead portion comprising a spherical portion 43 and a correspondingspherical surface portion 42 located at the distal end of the device 5 cwhich provide a smooth, blunt contour outer surface. More specifically,as shown, the spherical portion 43 and spherical surface portion 42further provide a domed, hemisphere (i.e., less than a full sphere) andhemispherical surface portion comprising preferably about 180 degrees.

Also as shown in FIGS. 20-24, the enlarged head portion of electrode 25preferably also comprises a cylindrical portion 39 and a correspondingcylindrical surface portion 40 located proximal and adjacent to thespherical portion 43 and spherical surface portion 42, respectively.

Further continuing with FIGS. 20-24, electrode 25 preferably comprises aconnector portion, preferably comprising a shank 46, which connects theremainder of electrode 25 to the shaft 17. Among other things, theconnector portion of electrode 25 is preferably configured to form aconnection with a mating connector portion of the shaft 17. As shown,preferably the shank portion 46 is configured to extend into cavity 50of shaft 17 which comprises a cylindrical receptacle and provides themating connector portion for shank 46. More preferably, surface 48 ofthe shank portion 46 is configured to mate against and form aninterference fit with surface 52 of cavity 50 to provide the connection.

Continuing with FIGS. 20-24, shank portion 46 is preferably cylindricaland located proximal and adjacent to a neck portion 56. As shown, neckportion 56 comprises a cylindrical portion 57 (having a correspondingcylindrical surface portion 58) and a broadening portion 54 (having acorresponding broadening surface portion 47). Here broadening portion 54and corresponding broadening surface portion 47 are both spherical, andmore specifically comprise a domed, hemisphere and hemispherical surfaceportion comprising preferably about 180 degrees, located proximal andadjacent to the cylindrical portion 39 and cylindrical surface portion40.

Preferably, cylindrical portion 39 has a diameter in the range betweenand including about 1 mm to about 7 mm, although it has been found thatwhen cylindrical portion 39 is larger than about 4 mm or less than about2 mm, tissue treatment can be adversely effected (particularly tissuetreatment time) due to an electrode surface that is respectively eitherto large or to small. Thus, preferably the cylindrical portion 39 has adiameter in the range between and including about 2.5 mm to about 3.5mm, and more preferably, about 3 mm.

With respect to length, preferably cylindrical portion 39 has a lengthin the range between and including about 2 mm to about 8 mm, and morepreferably has a length in the range between and including about 3 mm toabout 5 mm. Even more preferably, cylindrical portion 39 has a length ofabout 4.5 mm.

As shown in FIGS. 20-24, the cylindrical portion 57 of neck portion 56preferably has a cross-sectional dimension, here diameter, greater thanthe cross-sectional dimension, here also diameter, of the shank 46. Inthis manner, in certain embodiments, the proximal end of the neckportion 56 may be located adjacent and in contact with the distal end 53of shaft 17. Preferably, cylindrical portion 57 has a diameter in therange between and including about 2 mm to about 2.5 mm and the shank 46has a diameter in the range between and including about 1.4 mm to about1.9 mm. More preferably, cylindrical portion 57 has a diameter of about2.2 mm and the shank 46 has a diameter of about 1.6 mm.

With respect to length, preferably cylindrical portion 57 has a lengthin the range between and including about 1 mm to about 8 mm, and morepreferably has a length in the range between and including about 3 mm toabout 5 mm. Even more preferably, cylindrical portion 57 has a length ofabout 4 mm. Shank 46 preferably has a length in the range between andincluding about 2 mm to about 6 mm, and more preferably has a length inthe range between and including about 2.5 mm to about 5 mm. Even morepreferably, shank 46 has a length of about 3 mm.

Also as shown in FIGS. 20-24, electrode 25 comprises at least one recess64 which provides an elongated fluid flow channel for the distributionof fluid 24. The use of device 5 c, and in particular recesses 64, forthe distribution of fluid 24 is generally preferred to the fluid exitholes 93, 94 of device 5 b in particularly deep tissue crevices 97.

As shown, electrode 25 preferably comprises a plurality oflongitudinally directed recesses 64 and, more specifically, fourrecesses 64 equally spaced 90 degrees around the shank 46 and/or neckportion 56, both proximal of cylindrical portion 39. As best shown inFIG. 24, in certain embodiments, the recess 64 may comprise a first sidewall 64 a, a second opposing side wall 64 b, and a bottom wall 64 c.Preferably, recess 64 has a width in the range between and includingabout 0.1 mm to about 0.6 mm, and more preferably has a width of about0.4 mm.

In use, when tissue 32 overlies and occludes the fluid outlet opening 55of recess 64 for a portion of its longitudinal length, thus inhibitingfluid 24 from exiting therefrom, fluid 24 from recess 64 may still beexpelled from the electrosurgical device 5 c after flowinglongitudinally in the channel 64 to a remote location where the channel64 is unoccluded and uninhibited to fluid flow exiting therefrom.

On very rare occasion, it may be possible that the recess 64 may beoccluded by tissue 32 completely along its longitudinal length, thuscompletely inhibiting fluid flow from exiting through opening 55. Inorder to overcome this problem, at least a portion of electrode 25 maycomprise a material pervious to the passage of fluid 24, therethrough,such as a porous material described above.

Of the monopolar devices disclosed herein, device 5 c has been found tobe particularly useful to a surgeon performing a liver resection. Oncethe outer capsule of the liver is scored with a dry bovie blade alongthe planned line of resection, the distal tip of tip portion 45 ispainted back and forth along the line, with radio frequency power andthe flow of fluid 24 on, resulting in coagulation of the liverparenchyma. Once the tissue is coagulated under and around the electrodesurface 42 and, as the device 5 c enters crevice 97 as shown in FIG. 22,surfaces 40 and 42 of electrode 25 are used to blunt dissect thecoagulated parenchyma. Blunt dissection of the coagulated parenchyma isperformed by continuous abrading or splitting apart of the parenchymawith the substantially the same back and forth motion as coagulation andwith the device 5 c being held substantially in the same orientation asfor coagulation of the liver parenchyma. However, with blunt dissection,the surgeon typically applies more force to the tissue. In variousembodiments, once the liver parenchyma is coagulated, blunt dissectionmay be performed with or without the radio frequency power (i.e., on oroff) and/or with or without the presence of fluid 24.

As shown in FIG. 25, in another embodiment of the electrosurgical deviceof the present invention, as shown at reference character 5 d in FIG.25, the walls 64 a, 64 b of recess 64, surface 48 of the shank portion46, and/or the surfaces of the neck portion 56 of electrode 25 may beporous and connected by a plurality of tortuous pathways 59 in theporous material. Consequently, rather than flowing out of recess 64 froma direct fluid outlet opening 55, which may be occluded by tissue 32,the fluid 24 may exit indirectly from recess 64 by first flowing throughtortuous pathways 59 of electrode 25 from side walls 64 a, 64 b of therecess 64 and then exit electrode 25 from surface 58, which may be inunoccluded by tissue 32. Alternatively, if adjacent surface 58 ofelectrode 25 is also occluded by tissue 32, the fluid 24 may continue toflow through tortuous pathways 59 of electrode 25 and exit electrode 25from a surface 64 a, 64 b of a recess 64 or surface such as 40, 42, 47or 58 which may be in unoccluded by tissue 32.

Where electrode 25 comprises a porous material, recess 64 may be eithersupplemented with or replaced by the plurality of tortuous,interconnected passages 59 formed in the porous material as shown inFIG. 25. All or a portion of the electrodes can be porous according tothe invention.

In other embodiments of the invention, recess 64 may comprisecross-sectional shapes other than rectangular shapes. For example, asshown in FIGS. 26-28 recess 64 comprises a semi-circular shape, aV-shape, or a U-shape respectively, or any combination thereof.

Returning to FIG. 21, in order to facilitate direct fluid communicationof recess 64 with lumen 23 of shaft 17, preferably recesses 64 of device5 c are initiated within the confines of shaft 17. In other words,within the cavity 50 of shaft 17 proximal to distal end 53. As indicatedabove, the use of device 5 c, and in particular recesses 64, for thedistribution of fluid 24 is generally preferred to the fluid exit holes93, 94 of device 5 b in deep tissue crevices 97 where tissue 32 canocclude fluid flow from the fluid exit holes 93, 94 located in thecylindrical portion 39 of electrode 25. Also, since holes 93, 94 are notpresented with a declogging mechanism, such as provided for such asfluid exit holes 26 and 85, holes such as 93, 94 that can be simplyoccluded by ordinary tissue/electrode contact will sooner or laterbecome irreversibly clogged.

As shown in FIG. 21, with device 5 c fluid outlet openings 73 areprovided by the structure of electrode 25 (i.e., recesses 64) at thedistal end 53 of the shaft 17 which are protected and sheltered fromcontact and occlusion from surface 22 of tissue 32. Fluid outletopenings 73 of device 5 c are protected from occlusion from surface 22of tissue 32 as the structure of device 5 c defining the openings 26 isat least partially configured for non-contact with surface 22 of tissue32. More specifically, here the structure of the device defining theopenings 73 is completely configured for non-contact with surface 22 oftissue 32. Stated another way, the openings 73 are provided on thedevice 5 c at a location removed from the tissue surface 22. Also, asshown, openings 26 are particularly sheltered from occlusion fromsurface by 22 of tissue 32 by a portion of the shaft 17. Also as shown,openings 73 are formed substantially perpendicular to the surface 22 oftissue 32 and thus turned away from direct contact with surface 22 oftissue 32.

Another tip portion of an exemplary electrosurgical device 5 e of thepresent invention which may be used in conjunction with the system ofthe present invention is shown at reference character 45 in FIGS. 29-30.As shown, the broadening portion 54 has been eliminated and thecylindrical portion 39 has an equal cross-sectional dimension, herediameter, with the neck portion 56. Conversely, for device 5 c, thecylindrical portion 39 has a cross-sectional dimension, there alsodiameter, greater than the cross-sectional dimension, there alsodiameter, of the neck portion 56.

Also as shown, the cylindrical portion 39 further comprises arectilinear cylindrical portion 39 a having a rectilinear cylindricalsurface portion 40 a and a curvilinear cylindrical portion 39 b having acurvilinear cylindrical surface portion 40 b. As shown, device 5 ecomprises the shape of a hockey stick. The cylindrical portion 39 fordevice 5 c may be similarly arranged.

Another tip portion of an exemplary electrosurgical device 5 f of thepresent invention which may be used in conjunction with the system ofthe present invention is shown at reference character 45 in FIGS. 31-32.As shown, the cylindrical portion 39 has a cross-sectional dimension,here diameter, less than the cross-sectional dimension, here alsodiameter, of the neck portion 56. As shown the neck portion 56 includesa narrowing portion 49 with a corresponding narrowing surface portion51, here both conical.

Also as shown, the cylindrical portion 39 further comprises arectilinear cylindrical portion 39 a having a rectilinear cylindricalsurface portion 40 a and a curvilinear cylindrical portion 39 b having acurvilinear cylindrical surface portion 40 b. Furthermore, as shown, thecylindrical portion 39, and more specifically at least one of therectilinear cylindrical portion 39 a and the curvilinear cylindricalportion 39 b, comprises a portion of a hook. Preferably, as shown boththe rectilinear cylindrical portion 39 a and the curvilinear cylindricalportion 39 b comprise portions of a hook. As shown, the hook furthercomprises an L-hook.

Another tip portion of an exemplary electrosurgical device 5 g of thepresent invention which may be used in conjunction with the system ofthe present invention is shown at reference character 45 in FIGS. 33-34.Similar to devices 5 c-5 f, the separate sleeve 82 of embodiments 5 aand 5 b has been eliminated from tip portion 45 of device 5 g.Consequently, the contact element, still preferably comprising anelectrode 25, is assembled directly with the shaft 17. Electrode 25 ispreferably assembled (e.g., mechanically connected via a press fit, orinterference fit, adjacent the distal end 53 of shaft 17.

As shown in FIGS. 33-34, electrode 25 preferably comprises a sphericalportion 43 and a corresponding spherical surface portion 42 located atthe distal end of the device 5 g, which provided a smooth, blunt contourouter surface. More specifically, as shown, the spherical portion 43 andspherical surface portion 42 further provide a domed, hemisphere (i.e.,less than a full sphere) and hemispherical surface portion comprisingpreferably about 180 degrees.

Also as shown in FIGS. 33-34, electrode 25 preferably also comprises anarrowing portion 49 and a corresponding narrowing surface portion 51,here both conical, located proximal and adjacent to the sphericalportion 43 and spherical surface portion 42, respectively. Morepreferably, as shown narrowing portion 49 and corresponding narrowingsurface portion 51 comprise a conical portion in the form of aconcentric cone shape, as opposed to device 5 f where the conicalportion provided by narrowing portion 49 and a corresponding narrowingsurface portion 51 comprises an eccentric cone shape. Thus, in the abovemanner, spherical portion 43 and spherical surface portion 42 mayprovide a blunt apex to narrowing portion 49 and a correspondingnarrowing surface portion 51, respectively.

Continuing with FIGS. 33-34, electrode 25 preferably also comprises acylindrical portion 39 and a corresponding cylindrical surface portion40 located proximal and adjacent to the narrowing portion 49 andnarrowing surface portion 51, respectively.

Similar to devices 5 c-5 f, electrode 25 preferably comprises aconnector portion, preferably comprising a shank 46, which connects theremainder of electrode 25 to the shaft 17. Among other things, theconnector portion of electrode 25 is preferably configured to form aconnection with a mating connector portion of the shaft 17. As shown,preferably the shank portion 46 is configured to extend into cavity 50of shaft 17 which comprises a cylindrical receptacle and provides themating connector portion for shank 46. More preferably, surface 48 ofthe shank portion 46 is configured to mate against and form aninterference fit with surface 52 of cavity 50 to provide the connection.Also similar to devices 5 c-5 f, shank portion 46 is preferablycylindrical and located proximal and adjacent to a neck portion 56.

As shown, similar to device 5 c, neck portion 56 comprises a cylindricalportion 57 (having a corresponding cylindrical surface portion 58) and abroadening portion 54 (having a corresponding broadening surface portion47). Here broadening portion 54 and corresponding broadening surfaceportion 47 are both spherical, and more specifically comprise a domed,hemisphere and hemispherical surface portion comprising preferably about180 degrees, located proximal and adjacent to the cylindrical portion 39and cylindrical surface portion 40.

Similar to devices 5 c-5 f, the cylindrical portion 57 of neck portion56 of device 5 g preferably has a cross-sectional dimension, herediameter, greater than the cross-sectional dimension, here alsodiameter, of the shank 46. In this manner, in certain embodiments, theproximal end of the neck portion 56 may be located adjacent and incontact with the distal end 53 of shaft 17.

Also similar to devices 5 c-5 f, preferably electrode 25 comprises atleast one recess 64 which provides an elongated fluid flow channel forthe distribution of fluid 24. As shown, electrode 25 preferablycomprises a plurality of longitudinally directed recesses 64 and, morespecifically, four recesses 64 equally spaced 90 degrees around theshank 46 and/or neck portion 56, both proximal of cylindrical portion39.

Another tip portion of an exemplary electrosurgical device 5 h of thepresent invention which may be used in conjunction with the system ofthe present invention is shown at reference character 45 in FIGS. 35-36.Device 5 h is similar to device 5 g in all respects except thatspherical portion 43 and spherical surface portion 42 have beeneliminated and replaced with a distal end sharp point 71.

As shown in FIG. 36, the electrode 25 of device 5 h comprises a simplecone. In other embodiments, electrode 25 may comprise other cone shapes.For example, as shown in FIGS. 37-40, the cone shape may comprise angive cone shape, an elliptical (prolate hemispheroid) cone shape, abi-conic cone shape and parabolic series cone shapes, respectively,which all may be defined by mathematical equations as known in the art.Still other cone shapes may include power series cone shapes, Haakeseries cone shapes, Sears-Haake and Von Karman, which all may be definedby mathematical equations as known in the art.

Certain embodiments of the invention may be particularly configured forbipolar devices. For example, an exemplary bipolar electrosurgicaldevice of the present invention which may be used in conjunction withthe system of the present invention is shown at reference character 5 iin FIGS. 41-43. With a bipolar device, the ground pad electrode locatedon the patient is eliminated and replaced with a second electrical poleas part of the device. An alternating current electrical circuit is thencreated between the first and second electrical poles of the device.Consequently, alternating current no longer flows through the patient'sbody to the ground pad electrode, but rather through a localized portionof tissue preferably between the poles of the bipolar device.

In certain embodiments, an exemplary bipolar surgical device of thepresent invention may comprise, among other things, multiple,substantially parallel, arms. As shown in FIG. 41, electrosurgicaldevice 5 i preferably includes two arms comprising rigid,self-supporting, hollow shafts 17 a, 17 b, a proximal handle comprisingmating handle portions 20 a, 20 b and arm tip portions as shown bycircles 45 a, 45 b. In this embodiment, shafts 17 a, 17 b preferablycomprise thick walled hypo-tubing. In this manner, the shafts 17 a, 17 bhave sufficient rigidity to maintain their form during use of the devicewithout kinking or significant bending.

Preferably the arms of device 5 i (comprising shafts 17 a, 17 b) areretained in position relative to each other by a mechanical couplingdevice comprising a collar 95 and inhibited from separating relative toeach other. Collar 95 preferably comprises a polymer (e.g.,acrylonitrile-butadiene-styrene or polycarbonate) and is preferablylocated on the distal portion of the arms. More preferably, the collar95 is located proximal the distal ends 53 a, 53 b of the shafts 17 a, 17b. Preferably the collar 95 comprises two apertures 96 a, 96 b,preferably comprising opposing C-shapes, configured to receive a portionof the shafts 17 a, 17 b which are preferably snap-fit therein. Once thecollar 95 is connected to the shafts 17 a, 17 b, preferably by asnap-fit connection, the collar 95 may be configured to slide along thelength of the shafts 17 a, 17 b as to adjust or vary the location of thecollar 95 on the shafts 17 a, 17 b. Alternatively, the location of thecollar 95 may be fixed relative to the shafts 17 a, 17 b by welding, forexample.

Device 5 i comprises a first arm tip portion 45 a and a second arm tipportion 45 b. As shown, preferably both first arm tip portion 45 a andsecond arm tip portion 45 b are each individually configured identicalto tip portion 45 of device 5 a. As a result, device 5 i has twoseparate, spatially separated (by empty space) contact elementspreferably comprising electrodes 25 a, 25 b.

As shown in FIG. 42, when device 5 i is in use electrodes 25 a, 25 b arelaterally spaced adjacent tissue surface 22 of tissue 32. Electrodes 25a, 25 b are connected to a source of alternating electrical current andalternating current electrical field is created between electrodes 25 aand 25 b. In the presence of alternating current, the electrodesalternate polarity between positive and negative charges with currentflow from the positive to negative charge.

Similar to device 5 a, for device 5 i fluid 24 is communicated from afluid source 1 within the lumens 23 a, 23 b of the shafts 17 a, 17 bthrough the lumens 89 a, 89 b and cavities 81 a, 81 b of the sleeves 82a, 82 b where it is expelled from around and on the surface 42 a, 42 bof the electrodes 25 a, 25 b.

As with use of device 5 a, with use of device 5 i fluid couplings 30 a,30 b preferably comprising discrete, localized webs and more preferablycomprising a triangular shaped web or bead portion providing a film offluid 24 between surface 22 of tissue 32 and electrodes 25 a, 25 a. Whenthe user of electrosurgical device 5 i places electrodes 25 a, 25 b at atissue treatment site and moves electrodes 25 a, 25 b across surface 22of tissue 32, fluid 24 is expelled around and on surfaces 42 a, 42 b ofelectrodes 25 a, 25 b at the distal ends 83 a, 83 b of sleeves 82 a, 82b and onto surface 22 of tissue 32 via couplings 30 a, 30 b. At the sametime, RF electrical energy, shown by electrical field lines 130, isprovided to tissue 32 at tissue surface 22 and below tissue surface 22into tissue 32 through fluid couplings 25 a, 25 b.

As with device 5 a, the fluid 24, in addition to providing an electricalcoupling between the electrosurgical device 5 i and tissue 32,lubricates surface 22 of tissue 32 and facilitates the movement ofelectrodes 25 a, 25 b across surface 22 of tissue 32. During movement ofelectrodes 25 a, 25 b, electrodes 25 a, 25 b typically slide across thesurface 22 of tissue 32, but also may rotate as electrodes 25 a, 25 bmove across surface 22 of the tissue 32. Typically the user ofelectrosurgical device 5 i slides electrodes 25 a, 25 b across surface22 of tissue 32 back and forth with a painting motion while using fluid24 as, among other things, a lubricating coating. Preferably thethickness of the fluid 24 between the distal end surface of electrodes25 a, 25 b and surface 22 of tissue 32 at the outer edge of couplings 30a, 30 b is in the range between and including about 0.05 mm to 1.5 mm.More preferably, fluid 24 between the distal end surface of electrodes25 a, 25 b and surface 22 of tissue 32 at the outer edge of coupling 30a, 30 b is in the range between and including about 0.1 mm to 0.3 mm.Also preferably, in certain embodiments, the distal end tip of electrode25 contacts surface 22 of tissue 32 without any fluid 24 in between.

As shown in FIG. 43, the fluid coupling for device 5 i may comprise aconductive fluid bridge 27 between electrodes 25 a, 25 b which rests onsurface 22 of tissue 32 and forms a shunt between electrodes 25 a, 25 b.Given this scenario, a certain amount of RF energy may be diverted fromgoing into tissue 32 and actually pass between electrodes 25 a, 25 b viathe conductive fluid bridge 27. This loss of RF energy may slow down theprocess of coagulating tissue and producing the desired hemostasis oraerostasis of the tissue.

In order to counteract the loss of energy through bridge 27, once enoughenergy has entered bridge 27 to boil fluid 24 of bridge 27, the loss ofRF energy correspondingly decreases with the loss of bridge 27.Preferably energy is provided into fluid 24 of bridge 27 by means ofheat dissipating from tissue 32.

Thus, where a high % boiling of conductive fluid 24 of bridge 24 iscreated, the loss of RF energy through bridge 27 may either be reducedor eliminated because all the fluid 24 of bridge 27 boils off or a largefraction of boiling creates enough disruption in the continuity ofbridge 27 to disrupt the electrical circuit through bridge 27. Thus, onecontrol strategy of the present invention is to reduce the presence of aconductive fluid shunt by increasing the % boiling of the conductivefluid.

Bipolar device 5 i is particularly useful as non-coaptive tissue sealerand coagulator given it does not grasp tissue. Device 5 i isparticularly useful to surgeons to achieve hemostasis after dissectingthrough soft tissue as part of hip or knee arthroplasty. The tissuetreating portions can be painted over the raw, oozing surface 22 oftissue 32 to seal the tissue 32 against bleeding, or focused onindividual larger bleeding vessels to stop vessel bleeding.

Bipolar device 5 i is also useful to stop bleeding from the surface ofcut bone tissue as part of any orthopaedic procedure that requires boneto be cut. Device 5 i is particularly useful for these applications overmonopolar device 5 a as a much greater surface area 22 of tissue 32 maybe treated in an equivalent period of time and with better controlleddepth of the treatment.

As is well known, bone, or osseous tissue, is a particular form of denseconnective tissue consisting of bone cells (osteocytes) embedded in amatrix of calcified intercellular substance. Bone matrix mainly containscollagen fibers and the minerals calcium carbonate, calcium phosphateand hydroxyapatite. Among the many types of bone within the human bodyare compact bone and cancellous bone. Compact bone is hard, dense bonethat forms the surface layers of bones and also the shafts of longbones. It is primarily made of haversian systems which are covered bythe periosteum. Compact bone contains discrete nutrient canals throughwhich blood vessels gain access to the haversian systems and the marrowcavity of long bones. For example, Volkmann's canals which are smallcanals found in compact bone through which blood vessels pass from theperiosteum and connect with the blood vessels of haversian canals or themarrow cavity. Bipolar device 5 i disclosed herein may be particularlyuseful to treat compact bone and to provide hemostasis and seal bleedingvessels (e.g. by shrinking to complete close) and other structuresassociated with Volkmann's canals and Haversian systems.

In contrast to compact bone, cancellous bone is spongy bone and formsthe bulk of the short, flat, and irregular bones and the ends of longbones. The network of osseous tissue that makes up the cancellous bonestructure comprises many small trabeculae, partially enclosing manyintercommunicating spaces filled with bone marrow. Consequently, due totheir trabecular structure, cancellous bones are more amorphous thancompact bones, and have many more channels with various blood cellprecursors mixed with capillaries, venules and arterioles. Bipolardevice 5 i disclosed herein may be particularly useful to treatcancellous bone and to provide hemostasis and seal bleeding structuressuch as the above micro-vessels (i.e. capillaries, venules andarterioles) in addition to veins and arteries. Device 5 i may beparticularly useful for use during orthopedic knee, hip, shoulder andspine procedures (e.g. arthroplasty).

During a knee replacement procedure, the condyle at the distal epiphysisof the femur and the tibial plateau at the proximal epiphysis of thetibia are often cut and made more planer with saw devices to ultimatelyprovide a more suitable support structure for the femoral condylarprosthesis and tibial prosthesis attached thereto, respectively. Thecutting of these long bones results in bleeding from the cancellous boneat each location. In order to seal and arrest the bleeding from thecancellous bone which has been exposed with the cutting of epiphysis ofeach long bone, bipolar device 5 i may be utilized. Thereafter, therespective prostheses may be attached.

Turning to a hip replacement procedure, the head and neck of the femurat the proximal epiphysis of the femur is removed, typically by cuttingwith a saw device, and the intertrochantic region of the femur is mademore planer to provide a more suitable support structure for the femoralstem prosthesis subsequently attached thereto. With respect to the hip,a ball reamer is often used to ream and enlarge the acetabulum of theinnominate (hip) bone to accommodate the insertion of an acetabular cupprosthesis therein, which will provide the socket into which the head ofthe femoral stem prosthesis fits. The cutting of the femur and reamingof the hip bone results in bleeding from the cancellous bone at eachlocation. In order to seal and arrest the bleeding from the cancellousbone which has been cut and exposed, bipolar device 5 i may be utilized.Thereafter, as with the knee replacement, the respective prostheses maybe attached.

Bipolar device 5 i may be utilized for treatment of connective tissues,such as for shrinking intervertebral discs during spine surgery.Intervertebral discs are flexible pads of fibrocartilaginous tissuetightly fixed between the vertebrae of the spine. The discs comprise aflat, circular capsule roughly an inch in diameter and about 0.25 inchthick, made of a tough, fibrous outer membrane called the annulusfibrosus, surrounding an elastic core called the nucleus pulposus.

Under stress, it is possible for the nucleus pulposus to swell andherniate, pushing through a weak spot in the annulus fibrosus membraneof the disc and into the spinal canal. Consequently, all or part of thenucleus pulposus material may protrude through the weak spot, causingpressure against surrounding nerves which results in pain andimmobility.

Bipolar device 5 i may be utilized to shrink protruding and herniatedintervertebral discs which, upon shrinking towards normal size, reducesthe pressure on the surrounding nerves and relieves the pain andimmobility. Device 5 i may be applied via posterior spinal access undersurgeon control for either focal shrinking of the annulus fibrosusmembrane.

Where a intervertebral disc cannot be repaired and must be removed aspart of a discectomy, device 5 i may be particularly useful to seal andarrest bleeding from the cancellous bone of opposing upper and lowervertebra surfaces (e.g. the cephalad surface of the vertebral body of asuperior vertebra and the caudad surface of an inferior vertebra). Wherethe disc is removed from the front of the patient, for example, as partof an anterior, thoracic spine procedure, device 5i may also beparticularly useful to seal and arrest bleeding from segmental vesselsover the vertebral body.

Bipolar device 5 i may be utilized to seal and arrest bleeding ofepidural veins, which bleed as a result of the removal of tissue aroundthe dural membrane during, for example, a laminectomy or otherneurosurgical surgery. The epidural veins may start bleeding when thedura is retracted off of them as part of a decompression. Also during alaminectomy, device 5 i may be used to seal and arrest bleeding from thevertebral arch and, in particular the lamina of the vertebral arch.

As already discuss with respect to FIG. 6, even when general-purposegenerator 6 is set to a predetermined “fixed” power output, the actualpower delivered from generator 6 may be significantly different if theimpedance is outside the range defined by of the generator's low andhigh impedance cut-off limits.

Also with respect to FIG. 6, the output power is identified as being setto 75 watts in the generator's bipolar mode of operation. With respectto general-purpose generators 6 currently used in the electrosurgicalindustry, it has been found that a significant portion of the generatorsonly provide an output power of 50 watts in their bipolar mode, withonly a few providing an output power of 70-75 watts in bipolar mode.Above 75 watts, a very small number of generators may provide power intheir bipolar mode of 100 watts.

As is well known, the maximum output power of a general-purposegenerator 6 in its bipolar mode of operation is lower than the maximumoutput power of the generator in its monopolar mode of operation. Onereason for this is that the electrodes commonly associated with abipolar device are generally in much closer in proximity as compared tothe active and return electrodes of a monopolar device, thus reducingthe need for greater power. Furthermore, with additional power, use ofmany prior art dry tip electrosurgical devices only leads to more tissuedesiccation, electrode sticking, char formation and smoke generation,thus further obviating the need for additional power.

However, as established above, bipolar device 5 i of the presentinvention inhibits such undesirable effects of tissue desiccation,electrode sticking, char formation and smoke generation, and thus do notsuffer from the same drawbacks as prior art dry tip electrosurgicaldevices.

It has been found that bipolar device 5 i is, in certain instances, ableto use significantly greater power than the output power currentgeneral-purpose generators offer in their accorded bipolar modes. Forexample, bipolar device 5 i may use greater power to treat bone in knee,hip, shoulder and spine surgeries where blood loss would traditionallybe particularly high thus necessitating a blood transfusion.

General-purpose generators may offer significantly greater output powerthan 75 watts when set in their monopolar modes. For example, inmonopolar “cut mode”, the maximum power output of the generator istypically in the range of 300 watts. However, in monopolar cut mode thevoltage and preferred impedance ranges are much greater than in bipolarmode. For example, with respect to impedance, an exemplary low impedancecut-off for a monopolar cut mode is about 200 ohms while an exemplarylow impedance cut-off for bipolar mode is about 25-50 ohms.

In order to reduce monopolar voltage and impedance ranges to desirablelevels for bipolar use, a transformer may be placed in series circuitconfiguration between the electrodes of bipolar device 5 i and themonopolar mode power output of the generator 6.

As shown in FIG. 41, without a transformer, cable 9 of bipolar device 5i may ordinarily comprise two insulated wires 21 a, 21 b connectable togenerator 6 via two banana (male) plug connectors 77 a, 77 b connectingdirectly to (female) plug receptacles 79 a, 79 b of the generator 6(shown in FIG. 45). As shown in FIG. 41, the banana plug connectors 77a, 77 b are each assembled with wires 21 a, 21 b within individualhousings 129 a, 129 b which are not connected relative to one anotherand may be referred to as “loose leads”. Consequently, in thisembodiment, the banana plug connectors 77 a, 77 b are independentlymovable relative to one another. An exemplary electrical configurationestablished between banana plug connectors 77 a, 77 b of device 5 i andbanana plug receptacle connectors 79 a, 79 b of generator 6 is furtherillustrated in FIG. 45. From the above, it should be understood that theuse of plug connectors and receptacle connectors, is merely exemplary,and that other types of mating connector configurations may be employed.

However, with the introduction of a transformer 310 to convert monopolaroutput power to voltage and impedance ranges associated with bipolaroutput power, preferably the wires 21 a, 21 b, plug connectors 77 a, 77b and transformer 310 are all assembled and provided in a single, commonhousing similar to housing 129 shown in FIG. 9, and better shown in FIG.57. In contrast to the previous embodiment, in this embodiment the plugconnectors are held in a fixed, predetermined position relative to oneanother. In this manner, the plug connectors can be tailored to fit onlythose generators 6 with receptacle connectors positioned to coincide ormatch up with the predetermined positions of the plug connectors.

To further illustrate the above, FIG. 46 illustrates an exemplaryelectrical configuration which may be associated between monopolardevice 5 a and generator 6. As shown in FIG. 46, in this embodiment thewiring within plug housing 129 of device 5 a is configured such thathand switch 15 a may be electrically coupled to the “coagulation mode”hand switching circuitry of generator 6. More specifically, as shownhand switch 15 a is electrically coupled to generator 6 upon theinsertion of hand switch plug connector 77 d of device 5 a into handswitch receptacle connector 79 d of generator 6.

In addition to plug connector 77 d, plug housing 129 also contains powerplug connector 77 c which may be electrically coupled to the monopolarpower receptacle connector 79 c of generator 6. As shown, upon insertionof power plug connector 77 c into power receptacle connector 79 c,electrode 25 is now coupled to the power output of generator 6.

As shown, the finally connection of device 5 a to generator 6 comprisesground pad receptacle connector 177 of ground pad 125 being insertedover ground pad plug connector 179 of generator 6.

Plug connectors 77 c, 77 d are provided in a single common housing 129to better and more easily direct the plug connectors 77 c, 77 d to theirpredetermined targeted plug receptacle connectors 79 c, 79 d by virtueof being held in a fixed, predetermined position relative to one anotherby plug housing 129 such that they can only coincide with receptacleconnectors 79 c, 79 d, respectively.

In other embodiments, as indicated by the dotted lines, the wiringwithin plug housing 129 of device 5 a may be configured such that handswitch 15 a is coupled to plug connector 77 e and plug receptacle 79 e,in which case hand switch 15 a is now electrically coupled to themonopolar “cut mode” of generator 6 rather than the coagulation mode.

Now, with use of a bipolar device 5 i, as shown in FIG. 47, housing 129now includes transformer 310 and monopolar device 5 a has been replacedwith bipolar device 5 i, now also including hand switch 15 a.Furthermore, as shown, hand switch 15 a is coupled to the monopolar cutmode of generator 6 by use of plug connector 77 e and plug receptacle 79e. In other embodiments, the hand switch 15 a may be eliminated as shownin FIG. 48 and foot switch 15 may be used alone.

The option between monoploar “coagulation mode” hand switching andmonopolar “cut mode” hand switching is driven by a number of factors.However, an overriding consideration is often output power. In monopolarcoagulation mode, the maximum output power of a general purposegenerator is typically about 120 watts, while in monopolar cut mode themaximum output power of the same general purpose generator is typicallyabout 300 watts. For use of the monopolar devices disclosed herein (e.g.5 a, 5 c), 120 watts maximum output power associated with coagulationmode has been found to be generally sufficient, thus precluding the needfor higher powers associated with cut mode. However, for the bipolardevice 5 i, when using power provided from the generator's monopolaroutput, the higher power associated with monopolar cut mode is generallymore desirable than the lower power associated with monopolarcoagulation mode.

In other embodiments, the transformer 310 may be provided as part of anin-line adaptor 312, as shown in FIGS. 44 and 49. In this embodiment,preferably the adapter 312 includes its own receptacle connectors 314 a,314 b on one side which are configured to receive plug connectors 77 a,77 b of device 5 i, and on the opposing side has its own plug connector316 c and ground pad receptacle connector 177 which are configured toconnect to receptacle connector 79 c and ground pad plug connector 179of generator 6, respectively. To further illustrate the above, FIG. 49illustrates an exemplary electrical configuration which may beassociated between bipolar device 5 i, adapter 312 and generator 6.

The adaptor 312 may also be configured to accommodate a bipolar devicewith a hand switch. Without adaptor 312, FIG. 50 shows an exemplaryelectrical configuration established between plug connectors 77 a, 77 bof device 5 i and receptacle connectors 79 a, 79 b of generator 6. Inaddition, FIG. 50 shows hand switch 15 a coupled to the hand switchingcircuitry of generator 6. More specifically, as shown hand switch 15 ais electrically coupled to generator 6 upon the insertion of bipolarhand switch plug connector 77 f of device 5 i into bipolar hand switchreceptacle connector 79 f of generator 6.

With adaptor 312, as shown in FIG. 51A and as with the earlierembodiment, preferably the adaptor 312 includes its own receptacleconnectors 314 a, 314 b on one side which are configured to receive plugconnectors 77 a, 77 b of device 5 i, and on the opposing side has itsown plug connector 316 c and ground pad receptacle connector 177 whichare configured to connect to receptacle connector 79 a and ground padplug connector 179 of generator 6, respectively. Furthermore, adaptor312 has its own bipolar hand switch receptacle connector 314 f on oneside configured to mate with the bipolar hand switch plug connector 77 fof device 5 i, and on the opposing side has its own monopolar handswitch plug connector 316 e configured to connect to monopolar “cutmode” hand switch receptacle connector 79 e of generator 6. Finally, inorder to establish the remaining link between the hand switch circuitryand the monopolar power output, the adaptor 312 has a hand switch plugconnector 314 g configured to mate with hand switch receptacle connector77 g of device 5 i.

As shown in FIG. 51A, bipolar device 5 i now includes four connectors(i.e. 77 a, 77 b, 77 f, 77 g) when adaptor 312 is used rather than justthe three connectors (i.e. 77 a, 77 b, 77 f) associated with FIG. 50.Connector 77 g is added to provide a connection, when mated withconnector 314 g of adaptor 312, to plug connector 316 c which bypassestransformer 310. This is required as the hand switch circuitry ofgenerator 6 typically utilizes direct current (DC) rather than thealternating current (AC) associated with the power circuitry.Consequently, since continuous DC will not cross between the primarycoil 318 and secondary coil 320 of transformer 310, this fourthconnection is required.

In other embodiments, bipolar device 5 i may return to the use of onlythree connectors with a modification of the electrical wiring withinadaptor 312. As shown in FIG. 51B, rather than bipolar hand switchreceptacle connector 314 f being electrically wired to connect tomonopolar hand switch plug connector 316 e as in FIG. 51A, bipolar handswitch receptacle connector 314 f is electrically wired to connect tomonopolar power plug connector 316 c, which ultimately connects tomonopolar power receptacle connector 79 c of generator 6. Furthermore,in addition to bipolar power receptacle connector 314 a beingelectrically wired to connect to the secondary coil 320 of transformer310, it is also electrically wired to connect to monopolar hand switchplug connector 316 e, which ultimately connects to monopolar “cut mode”hand switch receptacle connector 79 e of generator 6. In this manner,where direct current is utilized as part of the hand switch circuitry ofgenerator 6, the direct current is still provided a return electricalpath to the generator 6.

For the embodiment shown in FIG. 51B, the primary and secondary coils318, 320 are wound and/or wired (preferably both) such that thesecondary voltage V_(s) is electrically in-phase with the primaryvoltage V_(p). In other words, the secondary voltage V_(s) associatedwith secondary coil 320 rises and falls simultaneously with the primaryvoltage V_(p) associated with the primary coil 318. The black “dots”accompanying the primary and secondary coils 318, 320 are commonly usedto indicate points on a transformer schematic that have the sameinstantaneous polarity and are in-phase. On an oscilloscope, an“in-phase” relationship between the primary voltage V_(p) and thesecondary voltage V_(s) may be shown by the corresponding sine waveshaving the same frequency and their positive and negative peaksoccurring at the same time.

Turning to the specifics of transformer 310, preferably the transformer310 comprises primary and secondary coils 318, 320 comprising #18 magnetwire wound on a toroidal shaped, magnetic core 322. More preferably thecore 322 comprises a ferromagnetic core and even more preferably aferrite core. Preferably the ferrite has an amplitude permeability inthe range of 500μ to 5,000μ and more preferably of about 2,000μ. Morepreferably, the ferrite comprises ferrite material no. 77. Preferablythe core has a 1.4 inch outside diameter, a 0.9 inch inside diameter anda 0.5 inch thickness which is available from Coil Winding Specialists.

For a perfect transformer, that is, a transformer with a coefficient ofcoupling (k) equal to 1, the impedances can be described as follows:Z _(p) =Z _(s)(N _(p) /N _(s))²   (8)where:

-   -   Z_(p)=Impedance looking into the primary terminals from the        power source;    -   Z_(s)=Impedance of load connected to secondary;    -   N_(p)=Number of turns (windings) for primary coil; and

N_(s)=Number of turns (windings) for secondary coil

Based a primary impedance Z_(p)=200 ohms and a secondary impedance of25-50 ohms, the transformer 310 should be a step-down transformer with aturns ratio, N_(p)/N_(s), in the range between and including about3:1-2:1, respectively, and preferably about 2.5:1. This will result inpower being provided to the tissue in monopolar mode at much lowerimpedances (i.e. 25-50 ohms) than typically required for use of thegenerator's monopolar mode (i.e. 200 ohms).

Turning to voltage, the high impedance cut-off for bipolar mode at 75watts occurs at about 300 ohms, with the power remaining substantiallyunchanged between 25 ohms and 300 ohms. Thus, based on Ohm's law, for 75watts ohms and 300 ohms, the voltage before power begins to drop inbipolar mode is about 150 RMS volts. This now becomes the targetedvoltage from the monopolar mode with use of the transformer 310.

The high impedance cut-off for monopolar mode at 150 watts occurs atabout 1000 ohms. At 150 watts and 1000 ohms, the voltage in monopolarmode is about 387 RMS volts. With the transformer above, secondaryvoltage may be described as follows:V _(s) =V _(p)(N _(s) /N _(p))   (9)where:

-   -   V_(s)=Secondary voltage;    -   V_(p)=Primary voltage;    -   N_(p)=Number of turns (windings) for primary coil; and    -   N_(s)=Number of turns (windings) for secondary coil

Based on a primary voltage of 387 RMS volts, and a turns ratioN_(p)/N_(s) of 2.5:1, the secondary voltage is 155 RMS volts, which isonly slightly greater than the targeted 150 RMS volts. With respect tothe number of windings, in one embodiment preferably, the primary coil318 comprises 40 windings while the secondary coil 320 comprises 16windings resulting in the turns ratio of 2.5.

In yet another embodiment, as shown in FIGS. 52-56, electrosurgicaldevice 5 i may include a fluid flow control mechanism for turning fluidflow on and off to the tissue treating portion of the device, such as aroller pinch clamp assembly. As best shown in FIGS. 54-56, device 5 iincludes a roller pinch clamp assembly 242 and, more specifically, aninclined ramp roller pinch clamp assembly (as opposed to a parallelacting clamp).

As best shown in FIGS. 54-55, the clamp assembly 242 includes a housingprovided by handles 20 a, 20 b, a roller wheel 244 having a wheel centeraxis 246 and a guide pin hub. As shown, the guide pin hub is provided bypair of opposing, integrally formed, cylindrical trunnions 248 a, 248 b,but may also be provided by a separately formed pin. Trunnions 248 a,248 b are contained within and move along a track 250 preferablyprovided and defined by opposing trunnion channels 252 a, 252 b formedbetween wheel upper guide surfaces 254 a, 254 b and wheel lower guidesurfaces 256 a, 256 b extending longitudinally and parallel inward fromthe side wall portions of the handles 20 a, 20 b. As shown, wheel upperguide surfaces 254 a, 254 b are provided by a lip portion of the handles20 a, 20 b which partially define aperture 258 through which rollerwheel partially extends while wheel lower guide surfaces 256 a, 256 bare provided by ribs 260 a, 260 b.

Handles 20 a, 20 b also preferably provide tubing guide surfaces 272 a,272 b which at least a portion of which provide a clamping surfaceagainst which plastic tubing 4 b is clamped by roller 244. As best shownin FIGS. 54-55, tubing guide surfaces 272 a, 272 b are provided by ribs270 a, 270 b. In use, fluid line 4 b is externally squeezed andcompressed between the outer perimeter surface 262 of roller wheel 244and at least a portion of tubing guide surfaces 272 a, 272 b. In thisembodiment, preferably surface 262 is serrated.

Trunnions 248 a, 248 b support the movement of roller wheel 244 in twoopposing directions, here proximally and distally, along track 250. Asbest shown in FIGS. 55-56, the separation distance between the outerperimeter surface 262 of roller wheel 244 and tubing guide surfaces 272a, 272 b changes throughout the proximal and distal travel of rollerwheel 244 along track 250. More specifically, the separation distancebetween the outer perimeter surface 262 of roller wheel 244 and tubingguide surfaces 272 a, 272 b is greater between the outer perimetersurface 262 of roller wheel 244 and distal end portions 274 a, 274 b oftubing guide surfaces 272 a, 272 b provided by distal end portions 264a, 264 b of ribs 270 a, 270 b than between the outer perimeter surface262 of roller wheel 244 and proximal end portions 276 a, 276 b of tubingguide surfaces 272 a, 272 b provided by proximal end portions 266 a, 266b of ribs 270 a, 270 b.

As shown in FIGS. 54-55, when axis 246 of roller wheel 244 is opposingdistal end portions 274 a, 274 b of tubing guide surfaces 272 a, 272 b,preferably the separation distance is configured such that the tubing 4b may be uncompressed and the lumen of tubing 4 b completely open forfull flow therethrough. Conversely, as shown in FIG. 56, when axis 246of roller wheel 244 is opposing proximal end portions 276 a, 276 b oftubing guide surfaces 272 a, 272 b preferably the separation distance isconfigured such that the tubing 4 b is compressed and the lumen oftubing 4 b is completely blocked so that the flow of fluid throughtubing 4 b is prevented.

Distal end portions 274 a, 274 b of tubing guide surfaces 272 a, 272 bare separated from proximal end portions 276 a, 276 b of tubing guidesurfaces 272 a, 272 b by transition surfaces 278 a, 278 b which areprovided by transition rib portion 268 a, 268 b of ribs 270 a, 270 b.Preferably compression of tubing initially begins between transitionsurfaces 278 a, 278 b and the outer perimeter surface 262 of rollerwheel 244 and increases as wheel 244 moves proximally along proximal endportions 276 a, 276 b of tubing guide surfaces 272 a, 272 b. With thisconfiguration, consideration may be given to eliminating at least thatportion of distal end portions 274 a, 274 b of tubing guide surfaces 272a, 272 b that do not contribute to compression of the tubing 4 b.However, given that of distal end portions 274 a, 274 b of tubing guidesurfaces 272 a, 272 b guide tubing 4 b to splitter 240, such may not bedesirable.

As shown in FIGS. 54-56, both transition surfaces 278 a, 278 b andproximal end portions 276 a, 276 b of tubing guide surfaces 272 a, 272 bprovide sloped inclining surfaces proximally along their respectivelengths which decreases the separation distance between the outerperimeter surface 262 of roller wheel 244 and the tubing guide surfaces272 a, 272 b as the wheel 244 moves proximally. As shown, preferably thetransition surfaces 278 a, 278 b and proximal end portions 276 a, 276 bof tubing guide surfaces 272 a, 272 b have different slopes such thatthe separation distance decreases at a faster rate along transitionsurfaces 278 a, 278 b as compared to proximal end portions 276 a, 276 bof tubing guide surfaces 272 a, 272 b. In this manner, compression oftubing 4 b is non-linear along the length of travel of wheel 244 with amajority of the compression occurring between roller wheel 244 andtransition surfaces 278 a, 278 b. More preferably, the lumen of tubing 4b is completely blocked when roller wheel 244 is compressing the tubing4 b against the proximal portion of transition surfaces 278 a, 278 b,and the added compression of the tubing 4 b along proximal end portions276 a, 276 b of tubing guide surfaces 272 a, 272 b provides anadditional safety to assure complete blocking of the lumen even wherethere are variations in the tubing, such as the size of the lumen.

It should be realized that, due to the slope of the transition ribportion 268 a, 268 b, as the roller wheel 244 moves proximally relativeto transition surfaces 278 a, 278 b the lumen of tubing 4 b is blockedincrementally. Thus, in addition to providing an on/off mechanism, theroller pinch clamp assembly 242 can also be used to regulate the fluidflow rate between two non-zero flow values. It should also be realizedthat the roller pinch clamp assembly 242 of the device may be used inseries conjunction with another roller pinch clamp assembly which istypically provided as part of an IV set (i.e. IV bag, IV bag spike, dripchamber, connecting tubing, roller clamp, slide clamp, luer connector).When used in this manner, the roller pinch clamp assembly of the IV setmay be used to achieve a primary (major) adjustment for fluid flow rate,while the roller pinch clamp assembly 242 of the device may be used toachieve a secondary (more precise minor) adjustment for the fluid flowrate.

In another embodiment, as shown in FIGS. 57-59 for device 5 i, rollerwheel 244 of roller pinch clamp assembly 242 may be concealed from viewto reduce the possibility of foreign objects (e.g. practitioner's rubbergloves) from entering into the confines of handle 20 a, 20 b throughaperture 258 and getting snagged, for example, between the trunnions 248a, 248 b and track 250.

As shown in FIG. 57, roller wheel 244 is concealed from view by handleportions 20 a, 20 b. As shown, switch button 192 protrudes through anaperture 194 formed in handle portions 20 a, 20 b. Button 192 ispreferably integrally connected via a single piece polymer molding to aproximally extending switch arm 196 which provides a receptacle 306which contains and holds roller wheel 244.

With use of the fluid flow control mechanism of FIGS. 57-59, in responseto button 192 being moved proximally and distally in switch buttonaperture 194, switch arm 196 moves proximally and distally along track250, which correspondingly moves roller wheel 244 to compress tubing 4 bas discussed above.

As best shown in FIG. 59, preferably the fluid flow control mechanismfurther comprises a mechanism which may hold the arm 196 in a fixedposition while compressing and occluding fluid line 4 b. As shown,preferably the locking mechanism comprises detents 308 a, 308 b (308bnot shown) formed in handle portions 20 a, 20 b which partially receivetrunnions 248 a, 248 b therein to hold arm 196 in a fixed position.

The devices of the present invention may provide treatment of tissuewithout using a temperature sensor built into the device or a customspecial-purpose generator. In a preferred embodiment, there is nobuilt-in temperature sensor or other type of tissue sensor, nor is thereany custom generator. Preferably, the invention provides a means forcontrolling the flow rate to the device such that the device and flowrate controller can be used with a wide variety of general-purposegenerators. Any general-purpose generator is useable in connection withthe fluid delivery system and flow rate controller to provide thedesired power; the flow rate controller will accept the power andconstantly adjust the saline flow rate according to the controlstrategy. Preferably, the generator is not actively controlled by theinvention, so that standard generators are useable according to theinvention. Preferably, there is no active feedback from the device andthe control of the saline flow rate is “open loop.” Thus, in thisembodiment, the control of saline flow rate is not dependent onfeedback, but rather the measurement of the RF power going out to thedevice.

The use of the disclosed devices can result in significantly lower bloodloss during surgical procedures such as liver resections. Typical bloodloss for a right hepatectomy can be in the range of 500-1,000 cubiccentimeters. Use of the devices disclosed herein to performpre-transection coagulation of the liver can result in blood loss in therange of 50-300 cubic centimeters. Such a reduction in blood loss canreduce or eliminate the need for blood transfusions, and thus the costand negative clinical consequences associated with blood transfusions,such as prolonged hospitalization and a greater likelihood of cancerrecurrence. Use of the device can also provide improved sealing of bileducts, and reduce the incidence of post-operative bile leakage, which isconsidered a major surgical complication.

For purposes of the appended claims, the term “tissue” includes, but isnot limited to, organs (e.g. liver, lung, spleen, gallbladder), highlyvascular tissues (e.g. liver, spleen), soft and hard tissues(connective, bone, cancellous) and tissue masses (e.g. tumors).

While a preferred embodiment of the present invention has beendescribed, it should be understood that various changes, adaptations andmodifications can be made therein without departing from the spirit ofthe invention and the scope of the appended claims. The scope of theinvention should, therefore, be determined not with reference to theabove description, but instead should be determined with reference tothe appended claims along with their fall scope of equivalents.Furthermore, it should be understood that the appended claims do notnecessarily comprise the broadest scope of the invention which theApplicant is entitled to claim, or the only manner(s) in which theinvention may be claimed, or that all recited features are necessary.

1. An adaptor for electrically coupling between an electrosurgicalgenerator and a bipolar electrosurgical device, the adaptor comprising:a power input connector for coupling the adaptor with a monopolar modepower output connector of the electrosurgical generator; a groundconnector for coupling the adaptor with a ground connector of theelectrosurgical generator; a first and a second power output connector,each for coupling the adaptor with a first and a second bipolar modepower input connector of the bipolar electrosurgical device,respectively; a transformer coupled between the power input connectorand the first and second power output connectors; a monopolar handswitch connector for coupling the adaptor with a monopolar mode handswitch connector of the electrosurgical generator; and at least onebipolar mode hand switch connector for coupling the adaptor with abipolar mode hand switch connector of the electrosurgical device.
 2. Theadaptor according to claim 1 wherein: the transformer comprises a firstcoil and a second coil; the first coil adapted to be coupled to thegenerator; and the second coil adapted to be coupled to the bipolarelectrosurgical device.
 3. The adaptor according to claim 2 wherein: thefirst coil comprises a plurality of windings; the second coil comprisesa plurality of windings; and the number of first coil windings isgreater then the number of second coil windings.
 4. The adaptoraccording to claim 1 wherein: the transformer comprises a first coil anda second coil; the first coil is coupled at a first end to the powerinput connector of the adaptor; the first coil is coupled at a secondend to the ground connector of the adaptor; the second coil is coupledat a first end to the first power output connector of the adaptor; andthe second coil is coupled at a second end to the second power outputconnector of the adaptor.
 5. The adaptor according to claim 1 furthercomprising: a first and a second bipolar mode hand switch connector forcoupling the adaptor with a first and a second bipolar mode hand switchconnector of the electrosurgical device, respectively.
 6. The adaptoraccording to claim 5 wherein: the first bipolar mode hand switchconnector of the adaptor is coupled to the monopolar hand switchconnector of the adaptor; and the second bipolar mode hand switchconnector of the adaptor is coupled to the power input connector of theadaptor in parallel with the transformer.
 7. The adaptor according toclaim 1 wherein: the bipolar mode hand switch connector of the adaptoris coupled to the power input connector of the adaptor in parallel withthe transformer; and the first power output connector of the adaptor iscoupled to the monopolar hand switch connector of the adaptor.
 8. Theadaptor according to claim 1 wherein: the transformer comprises a firstcoil and a second coil; and the first coil and the second coil arearranged to have a primary voltage and a secondary voltage,respectively; in phase in the presence of an alternating electricalcurrent.
 9. An adaptor for electrically coupling between anelectrosurgical generator and a bipolar electrosurgical device, theadaptor comprising: a power input connector for coupling the adaptorwith a monopolar mode power output connector of the electrosurgicalgenerator; a ground connector for coupling the adaptor with a groundconnector of the electrosurgical generator; a first and a second poweroutput connector, each for coupling the adaptor with a first and asecond bipolar mode power input connector of the bipolar electrosurgicaldevice, respectively; a monopolar hand switch connector for coupling theadaptor with a monopolar mode hand switch connector of theelectrosurgical generator; and at least one bipolar mode hand switchconnector for coupling the adaptor with a bipolar mode hand switchconnector of the electrosurgical device.
 10. The adaptor according toclaim 1 further comprising: a transformer coupled between the powerinput connector and the first and second power output connectors. 11.The adaptor according to claim 10 wherein: the transformer comprises afirst coil and a second coil; the first coil adapted to be coupled tothe generator; and the second coil adapted to be coupled to the bipolarelectrosurgical device.